Before the arrival of the Slavonic peoples in the Balkans during the 6th century AD, the area now known as Montenegro was inhabited principally by the Illyrians.

During the Bronze Age, the Illirii, probably the southernmost Illyrian tribe of that time, that gave their name to the entire group were living near Skadar lake on the border of Albania and Montenegro and neighboring with the Greek tribes south. Along the seaboard of the Adriatic, the movement of peoples that was typical of the ancient Mediterranean world ensured the settlement of a mixture of colonists, traders, and those in search of territorial conquest. Substantial Greek colonies were established on the 6th and 7th centuries BC and Celts are known to have settled there in the 4th century BC. During the 3rd century BC, an indigenous Illyrian kingdom emerged with its capital at Scutari. The Romans mounted several punitive expeditions against local pirates and finally conquered the Illyrian kingdom in the 2nd century BC, annexing it to the province of Illyricum.

The division of the Roman Empire between Roman and Byzantine rule – and subsequently between the Latin and Greek churches – was marked by a line that ran northward from Shkodra through modern Montenegro, symbolizing the status of this region as a perpetual marginal zone between the economic, cultural, and political worlds of the Mediterranean. As Roman power declined, this part of the Dalmatian coast suffered from intermittent ravages by various semi-nomadic invaders, especially the Goths in the late 5th century and the Avars during the 6th century. These soon were supplanted by the Slavs, who became widely established in Dalmatia by the middle of the 7th century. Because the terrain was extremely rugged and lacked any major sources of wealth such as mineral riches, the area that is now Montenegro became a haven for residual groups of earlier settlers, including some tribes who had escaped Romanisation.

During the early Middle Ages, there were major political and demographic changes in the areas that belong to today's Montenegro. During the 6th and 7th centuries, Slavs, including Serbs, immigrated to Southeastern Europe. With the immigration of Serbian tribes, the first regional states were created in the wider area of ​​ancient Dalmatia, Prevalitana and other former provinces: Duklja, Travunija, Zahumlje and Neretlja principalities in the coastal areas and Principality of Serbia in the interior. During the early Middle Ages, the southern half of today's Montenegro belonged to the region of Duklja, that is, Zeta, while the northern half belonged to the then Principality of Serbia, which was ruled by the Vlastimirović dynasty. At the same time, the westernmost part of today's Montenegro belonged to Travunia.

In the second half of the 6th century, Slavs migrated from the Bay of Kotor to the River of Bojana and the hinterland of it as well as surround the Skadar lake. They formed the Principality of Doclea. Under the following missions of Cyril and Methodius, the population was Christianised. The Slavic tribes organised into a semi-independent dukedom of Duklja (Doclea) by the 9th century.

After facing subsequent Bulgarian domination, the people were split as the Doclean brother-archonts split the lands among each other after 900. Prince Časlav Klonimirović of the Serbian Vlastimirović dynasty extended his influence over Doclea in the 10th century. After the fall of the Serbian Realm in 960, the Docleans faced a renewed Byzantine occupation through to the 11th century. The local ruler, Jovan Vladimir Dukljanski, whose cult still remains in the Orthodox Christian tradition, was at the time struggling to ensure independence.

Stefan Vojislav started an uprising against the Byzantine domination and gained a huge victory against the army of several Byzantine strategoi in Tudjemili (Bar) in 1042, which put to an end the Byzantine influence over the Doclea. In the 1054 Great Schism, the Doclea fell on the side of the Catholic Church. Bar became a Bishopric in 1067. In 1077, Pope Gregory VII recognised Duklja as an independent state, acknowledging its King Mihailo (Michael, of the Vojislavljević dynasty founded by nobleman Stefan Vojislav) as Rex Doclea (King of Duklja). Later on Mihailo sent his troops, led by his son Bodin, in 1072 to assist the uprising of Slavs in Macedonia. In 1082, after numerous pleas the Bar Bishopric of Bar was upgraded to an Archbishopric.

The expansions of the Kings of the Vojislavljević dynasty led to the control over the other Slavic lands, including Zahumlje, Bosnia and Rascia. The might of the Doclea declined and they generally became subjected to the Grand Princes of Rascia in the 12th century. Stefan Nemanja was born in 1117 in Ribnica (today Podgorica). In 1168, as the Serbian Grand Zhupan, Stefan Nemanja took Doclea. In charters of Vranjina Monastery during the 14th century the ethnic groups which are mentioned were Albanians (Arbanas), Vlahs, Latins (Catholic citizen) and Serbs.

Jovan Vladimir or John Vladimir was the ruler of Duklja, the most powerful Serbian principality of the time, from around 1000 to 1016. He ruled during the protracted war between the Byzantine Empire and the Bulgarian Empire. Vladimir was acknowledged as a pious, just, and peaceful ruler. He is recognized as a martyr and saint, with his feast day being celebrated on 22 May.

Jovan Vladimir had a close relationship with Byzantium but this did not save Duklja from the expansionist Tsar Samuel of Bulgaria, who attacked Duklja around 997, John Vladimir retreated to the inaccessible mountain areas in the vicinity of Shkodër. Samuel conquered the principality around 1010 and took Vladimir prisoner. A medieval chronicle asserts that Samuel's daughter, Theodora Kosara, fell in love with Vladimir and begged her father for his hand. The tsar allowed the marriage and returned Duklja to Vladimir, who ruled as his vassal. Vladimir took no part in his father-in-law's war efforts. The warfare culminated with Tsar Samuel's defeat by the Byzantines in 1014 and death soon after. In 1016, Vladimir fell victim to a plot by Ivan Vladislav, the last ruler of the First Bulgarian Empire. He was beheaded in front of a church in Prespa, the empire's capital, and was buried there.

Prince Vladimir was succeeded by his nephew, Vojislav. Sources from Byzantium call him: Travunjanin and Dukljanin. After the failed first uprising against Byzantium, he was imprisoned in 1036 . in Constantinople, from where he fled, in 1037 or 1038. In Byzantine Duklja, he rebelled, attacking other tribes that recognized Byzantine rule. During his reign, the most significant event was the Battle of Bar, in 1042. In it, Prince Vojislav brought independence with a great victory over the Byzantine army. This Serbian principality has been called Zeta in Byzantine chronicles since then, and that name is gradually replacing the old one (Duklja). The consequence of the victory at Bar was that Duklja was one of the first Serbian countries to which Byzantium officially recognized state sovereignty and independence. According to the Bar genealogy, he ruled for 25 years. Until 1046, Duklja was ruled by five brothers, as regional lords, princes of individual parishes, under the supreme authority of the mother and the eldest Gojislav. In this period of the joint rule of the brothers, the oldest known official written contract in the Dukla state was created. The content of the contract concluded between the Dukljan princes, the brothers Mihailo (ruler of Oblik) and Sagenek (ruler of Gorska župa) is recounted in the Bar genealogy.

The Battle of Bar took place on October 7, 1042 between the army of Stefan Vojislav, the Serbian ruler of Duklja, and Byzantine forces led by Michaelus Anastasii. The battle was actually a sudden attack on the Byzantine camp in the mountain gorge, which ended in the utter defeat of the Byzantine forces and the deaths of 7 of their commanders (strategoi). Following the defeat and retreat of the Byzantines, Vojislav ensured a future for Duklja without imperial authority, and Duklja would soon emerge as the most significant Serb state.

After his mother's death, around 1046, Mihailo, the son of Prince Vojislav is proclaimed the lord (prince) of Duklja. He ruled for about 35 years, first as a prince, and then as a king. During his reign, the state continued to rise (the Byzantine emperor concluded a treaty of alliance and friendship with Duklja). During the reign of Michael, there was a church split in 1054, East-West Schism. This event took place ten years after the independence of Duklja, and the border line of the two Christian churches crossed the territory occupied by today's Montenegro. This border from 1054 followed the same imaginary line as in 395, when the Roman Empire split into East and West. After the schism of the Christian church, Prince Mihailo supported the greater independence of the Church in Zeta and the state's orientation towards the West. In 1077, Mihailo received the royal insignia (rex Sclavorum) from Pope Gregory VII, which also recognized Duklja as a kingdom. This event is depicted in the later era, during the reign of Nemanjić.

As the future heir of King Mihail, Bodin played a significant role in the uprisings against Byzantium in the Balkans, so during his reign, the influence and territorial area of ​​Duklja expanded to neighboring countries: Raška, Bosnia and Bulgaria. Namely, towards the end of the reign of King Michael, major changes in the balance of power on the Balkan Peninsula took place after 1071, the year of Byzantium's defeat at the Battle of Manzikert, as well as of the Norman conquest of southern Italy. King Mihailo was mentioned for the last time in 1081.

Constantine Bodin was a medieval king and the ruler of Duklja, the most powerful Serbian principality of the time, from 1081 to 1101. Born in peaceful times, when the Southern Slavs were subjects of the Byzantine Empire, his father was in 1072 approached by Bulgarian nobility, who sought aid in their revolt against the Byzantines; Mihailo sent them Bodin, who was crowned Bulgarian tsar under the name Petar III joined the short-lived revolt, being captured the following year after initial success. He was freed in 1078, and upon the death of his father in 1081 he succeeded to the throne of Dioclea (Dukla). Having renewed his acknowledgement of Byzantine overlordship, he soon sided with their enemies, the Normans. In April 1081 He married the Norman princess Jaquinta, daughter of Archiris, leader of the Norman party in Bari which led to a Byzantine invasion and his capture. Although he quickly had himself freed, his reputation and influence waned.

In 1085, when, taking advantage of the death of Robert Guiscard and the change of forces in the Balkans, he conquered the city of Durres and the entire Durres region from the rule of the Franks. As soon as he became king, he tried to expel his rivals, Radoslav's heirs from Duklja. After the peace concluded in this way, in 1083 or 1084, King Bodin undertook expeditions to Raška and Bosnia and annexed them to the kingdom of Duklja. In Raška, he appoints two prefects from his court: Vukan and Marko, from whom he receives a vassal oath. Due to his behavior in the Battle of Durres, the king of Duklja lost the trust of Byzantium. From the captured Durres, Byzantium began an offensive on Duklja and recovered the seized cities (small episcopal cities: Drivast, Sard, Spata, Baleč). Bodin was defeated and captured, although the location of the decisive battle is not known. After Bodin's death, the power of Dukla declined both territorially and politically.

At the time of Mihailo I, Zeta was a župa within Duklja and was also known as Luška župa. From the end of the 11th century, the name began to be used to refer to the whole of Duklja, at first in Kekaumenos's military manual, written in the 1080s. Over the following decades, the term Zeta gradually replaced Duklja to denote the region.

Serbian Prince Desa Urošević conquered Duklja and Travunia in 1148, combining the title as "Prince of Primorje" (the Maritime) and co-ruled Serbia with his brother Uroš II Prvoslav from 1149 to 1153, and alone until 1162. In 1190, Grand Župan of Rascia and Stefan Nemanja's son, Vukan II, asserted his right over Zeta. In 1219, Đorđe Nemanjić succeeded Vukan. He was succeeded by his second oldest son, Uroš I, who built the 'Uspenje Bogorodice' monastery in Morača.

Between 1276 and 1309, Zeta was ruled by Queen Jelena, widow of Serbia's King Uroš I. She restored around 50 monasteries in the region, most notably Saint Srđ and Vakh on the Bojana River. From 1309 to 1321, Zeta was co-ruled by the oldest son of King Milutin, Young King Stefan Uroš III Dečanski. Similarly, from 1321 to 1331, Stefan's young son Stefan Dušan Uroš IV Nemanjić, the future Serbian King and Emperor, co-ruled Zeta with his father.

Dušan the Mighty was crowned Emperor in 1331, and ruled until his death in 1355. Žarko held the Lower Zeta region: he is mentioned in records from 1356, when he raided some traders from Dubrovnik, not far from Sveti Srđ at Lake Skadar. Zeta itself was held by the widow of Dušan, Jelena, who at the time was in Serres where she had her court. The next year, in June, Žarko becomes a citizen of the Republic of Venice, where he was known as "baron lord of the Serbian King, with holdings in the Zeta region and Bojana of the maritime". Đuraš Ilijić was "Head" (Kefalija, from Greek Kephale) of Upper Zeta until his murder in 1362.

The Balšić family ruled Zeta, whose territory encompassed parts of present-day Montenegro and northern Albania, from 1356. In the mid-14th century, Zeta was divided into Upper and Lower Zeta, governed by magnates. After Stefan Dušan (r. 1331–55), his son Stefan Uroš V ruled Serbia during the fall of the Serbian Empire; a gradual disintegration of the Empire as a result of decentralization in which provincial lords gained semi-autonomy and eventually independence. The Balšići wrestled the Zeta region in 1356–1362, when they removed the two rulers in Upper and Lower Zeta. Ruling as lords, they empowered themselves and over the decades became an important player in Balkan politics.

Đurađ's rule extended from around 1362 to 1378. He had forged an alliance with King Vukašin Mrnjavčević, having married his daughter Olivera, until Mrnjavčević's fall at the Battle of Maritsa (1371). Đurađ I ran Zeta as a modern ruler of the time. Zeta's institutions were functioning well, while the coastal towns enjoyed considerable autonomy. Commerce was well developed and enhanced by the existence of Zeta's currency, the dinar. Đurađ I allied with his neighbors Prince Lazar Hrebeljanović of Serbia, Ban Tvrtko I Kotromanić of Bosnia, Prince Nikola I Gorjanski and King Louis I of Hungary, to defeat the ambitious Nikola Altomanović in 1373. In spite of this, the defeated and blinded Altomanović found refuge in Zeta until his death. While he was battling in the south of Kosovo, Đurađ's younger brother Balša II married Komnina, a close cousin of Emperor Stefan Dušan's wife, Jelena. Through the marriage, Đurađ II received a generous dowry in land, including Avlona, Berat, Kanina, and some additional strategically important regions. Upon the division of Altomanović's lands (in Herzegovina), the Balšićs took the towns of Trebinje, Konavle and Dračevica. Subsequent dispute over these towns led to a conflict between Zeta and Bosnia, led by Ban Tvrtko I. The fight was eventually won by Bosnia, supported by Hungary, after Đurađ's death in 1378.

In 1378, following Đurađ's death, his brother Balša II became the King of Zeta. In 1382, King Tvrtko I conquered Dračevica, and built the town later known as Herceg-Novi. Both Tvrtko I and Balša II aspired to ascend to the throne of the Nemanjić dynasty.

During his rule, Balša II's could not maintain the control of the feudal lords as his predecessor did. His power was strong only in region around Skadar, and in the eastern part of Zeta. The most prominent feudal lords who did not recognize Balša's rule was the House of Crnojević, who were consistent encouraged by the Venetians to rebel against him.

Balša II needed four attempts to conquer Drač, an important commercial and strategic center. Defeated, Karl Thopia appealed to the Turks for help. Turkish forces led by Hajrudin Pasha inflicted heavy damage to Balša II's forces and killed him at a major Battle of Savra near Lushnjë, in 1385.

The successor of Balša II, Đurađ II Stracimirović Balšić, ruled Zeta from 1385 to 1403; he was Balša's nephew and son of Stracimir. He also had difficulties controlling the local feudal lords, with no control over the fiefs of the entire Upper Zeta. In addition, the feudal lords around Onogošt (Nikšić) accepted the Venetian protection. The most prominent of those lords was Radič Crnojević, who controlled the area between Budva and Mount Lovćen. Moreover, a number of Arbanas feudal lords, particularly Lekë Dukagjini and Paul Dukagjini joined the conspiracy against Đurađ II.

With this in mind as well as the constant danger from the Turks, Đurađ II maintained strong family ties with the Serbia's main lord of the time, Prince Lazar. To help Prince Lazar defend the Serbian lands from Ottoman invasion, Đurađ II sent his troops along with Ban Tvrtko I Kotromanić's forces (with whom he had a dispute over Kotor) to meet the Ottoman army at Kosovo Polje. Despite Sultan Murad I's death, the Serbian army suffered a defeat at the epic Battle of Kosovo in 1389. According to the sources, Đurađ II did not participate in the battle, being in Ulcinj in Southern Zeta.

In later years, Đurađ II played skillful diplomatic games to enhance the rivalry between the Ottomans and the Venetians. To that purpose, he offered Skadar to both hoping that eventually he would be able to keep it. After two years of fighting, Turks and Venetians agreed to leave it to Đurađ II, who was neutral in the conflict. Similarly, the rivalry between Venetians and Hungarians brought a benefit to him. After a serious defeat of his forces by Turks near Nicopolis, the Hungarian King Sigismund gave him the title of Prince of Arbania and the control over the islands of Hvar and Korčula.

In the feud between Đurađ Branković and his uncle, Stefan Lazarević (son of Prince Lazar), who later received the title of Byzantine Despot, Đurađ II sided with Stefan. Due to Đurađ's support, Stefan defeated Turkish forces led by Đurađ Branković in the Battle of Tripolje on Kosovo Field in November 1402.

Venetian Albania was the official term for several possessions of the Republic of Venice in the southeastern Adriatic, encompassing coastal territories primarily in present-day southern Montenegro and partially in northern Albania.

Several major territorial changes occurred during the Venetian rule in those regions, starting from 1392, and lasting until 1797. By the end of the 15th century, the main possessions in northern Albania had been lost to the expansion of the Ottoman Empire. In spite of that, Venetians did not want to renounce their formal claims to the Albanian coast, and the term Venetian Albania was officially kept in use, designating the remaining Venetian possessions in coastal Montenegro, centred around the Bay of Kotor. During this period the Albanian Piracy was flourishing. Those regions remained under Venetian rule until the fall of the Republic of Venice in 1797. By the Treaty of Campo Formio, the region was transferred to the Habsburg monarchy.

In 1403, Đurađ II's 17-year-old son, Balša III, inherited the throne of Zeta after his father died as a consequence of the injuries he suffered in the Battle of Tripolje. As he was young and inexperienced, his main advisor was his mother Jelena, a sister of the Serbian ruler, Stefan Lazarević. Under her influence, Balša III declared Orthodox Christianity as the official state religion; however, Catholicism was tolerated.

Balša III continued the policies of his father. In 1418, took Skadar from the Venetians, but lost Budva. In the following year he made an unsuccessful attempt to recapture Budva. Afterwards he went to Belgrade to ask for help from Despot Stefan, but never returned to Zeta.

In 1421, before his death and under the influence of his mother Jelena, Balša III passed the rule of Zeta to Despot Stefan Lazarević. He fought Venetians and regained Bar in mid-1423, and in the following year he sent his nephew Đurađ Branković, who regained Drivast and Ulcinium (Ulcinj).

The Republic of Venice dominated the coasts of today's Montenegro from 1420 to 1797. In those four centuries the area around the Cattaro (Kotor) became part of Venetian Albania.

Zeta was united into the Serbian Despotate in 1421, after Balša III abdicated and passed the rule to his uncle, Despot Stefan Lazarević (maternally a Nemanjić).

Stefan I Crnojević consolidated his power in Zeta and ruled for 14 years, from 1451 until 1465. During his rule, he saw the Despotate completely subdued by the Ottomans soon after the death of Despot Đurađ Branković. Under Stefan Crnojević, Zeta comprised the Lovćen area around Cetinje, 51 municipalities which included the Crnojević River, the Zeta valley, and the tribes of Bjelopavlići, Pješivci, Malonšići, Piperi, Hoti, Kelmendi and others. The population of the territories controlled by Stefan was ca. 30,000, while the total population of the Zeta region (including territories under foreign rule) was ca. 80,000.

Capitalising on the weak position of Despot Đurađ, the Venetians and Herzog Stjepan Vukčić Kosača of St. Sava (the region of Herzegovina is named after him) conquered parts of his territory. Stefan I Crnojević, who had already established himself as the head of the Crnojević (around 1451) in Upper Zeta was forced to make territorial concessions. In addition, Kosača took Stefan's son Ivan as a political hostage, hoping it would force Stefan to side with him whenever needed.

Stefan married Mara, a daughter of a prominent Albanian Gjon Kastrioti, whose son was the Albanian national hero, Skanderbeg. In 1455, Stefan entered into an agreement with his ally Venice, stipulating that Zeta would recognize the nominal supremacy of Venice while maintaining its factual independence in virtually every respect. The agreement also stipulated that Zeta would assist Venice militarily on specific occasions in exchange for an annual provision. But in all other respects, Stefan's rule in Zeta was undisputed.

Ivan Crnojević became ruler of Zeta in 1465. His rule lasted until 1490. Immediately after taking the throne, Ivan attacked Venice, breaking the alliance his father had forged. He fought Venice in an attempt to capture Kotor. He had some success, gaining increasing support from the coastal Slavic tribes of Grbalj and Paštrovići in his quest to assert control over the Bay of Kotor. But when the Ottoman campaign in northern Albania and Bosnia convinced him that the main source of danger to his country was to the East, he sought a compromise with Venice. Ivan fought numerous battles against the Turks.

Zeta and Venice fought against the Ottoman Empire. The war ended with the successful defense of Shkodra, where Venetian, Shkodran, and Zetan defenders fought off forces of against Turkish Sultan Mehmed II and eventually won the war in 1474. However, the Ottomans besieged Shkodra again in 1478, with Mehmed II coming personally to lead that siege. After the Ottomans failed to take Shkodra by direct force, they assaulted Žabljak and took it without resistance. Venice ceded Shkodra to the sultan in 1479 in Treaty of Constantinople. Ivan had aspirations to organise an anti-Turkish alliance consisting of Napolitan, Venetian, Hungarian, and Zetan forces. However, his dream could not be fulfilled since the Venetians did not dare to help Ivan after their peace treaty with the Ottoman Empire in 1479. Left on his own, Ivan managed to preserve Zeta from frequent Ottoman offensives.

Knowing that the Ottomans would try to punish him for fighting on the Venetian side, and in order to preserve his independence, in 1482 he moved his capital from Žabljak on Lake Skadar to the mountainous area of Dolac, under Mount Lovćen. There he built the Orthodox Cetinje Monastery, around which the capital, Cetinje, would emerge. In 1496, Ottomans conquered Zeta and consolidated it into the newly established Sanjak of Montenegro, thereby ending its principality.

Đurađ IV Crnojević became ruler of Zeta in 1490. His rule lasted until 1496. Đurađ, Ivan's oldest son, was an educated ruler. He is most famous for one historical act: he used the printing press brought to Cetinje by his father to print the first books in southeastern Europe, in 1493. The Crnojević printing press marked the beginning of the printed word among South Slavs. The press operated from 1493 through 1496, turning out religious books, five of which have been preserved: Oktoih prvoglasnik, Oktoih petoglasnik, Psaltir, Molitvenik, and Četvorojevanđelje. Đurađ managed the printing of the books, wrote prefaces and afterwords, and developed sophisticated tables of Psalms with the lunar calendar. The books from the Crnojević press were printed in two colors, red and black, and were richly ornamented. They served as models for many books printed in Cyrillic.

After the rule of Zeta was handed to Đurađ, his youngest brother, Staniša, with no chance to succeed his father, Ivan, went to Constantinople and converted to Islam, receiving the name of Skender. As a loyal servant of the Sultan, Staniša became the Sanjak-bey of Shkodra. His brothers, Đurađ and Stefan II, continued the struggle against Ottomans. The historical facts are unclear and disputed, but it seems that the Venetians, frustrated by their own inability to subdue the House of Crnojević to their own interests, managed to kill Stefan II and deceitfully sent Đurađ to Constantinople. Principally, Đurađ visited Venice to work on the wide anti-Ottoman campaign, but was kept in captivity for some time while Stefan II was defending Zeta against the Ottomans. It is likely that upon his return to Zeta, Đurađ was kidnapped by the Venetian agents and sent to Constantinople under the accusation that he had been organizing a Holy War against Islam. There are some unreliable claims that Đurađ was given Anatolia to rule, but in any case the reports about Đurađ's whereabouts ceased after 1503.

In the fall of 1496, the Turkish sultan asked Đurđ Crnojević to immediately come to Constantinople to pay homage, or else to leave Montenegro. Finding himself in danger, Đurađ decided to defect under the protection of the Venetians. Immediately after taking possession of the land, the Turks created a separate vilayet of Crnojević on the territory of the former state of Crnojević, which was part of the Skadar Sanjak, and the first census of the newly created vilayet was carried out immediately after the establishment of the new government.

After the establishment of power, the Turks introduced taxes and spahic duties throughout the country, as in other parts of the empire. After the fall, Serbian Christians were exposed to various persecutions and oppression by Muslims, including the infamous system of "blood tribute", forced conversion, various Sharia laws inequalities, including forced labor, jizya , harsh taxation and slavery.

During the first years of Turkish rule, the Skadar sandjakbegs tried to consolidate direct Turkish rule in the Crnojević vilayet , but with considerable difficulties due to the growing Turkish-Venetian rivalry, which led to the official outbreak of the Venetian-Turkish war (1499-1503) in 1499 . It became obvious that among the conquered population there was a desire to cooperate with the Venetians in order to liberate them from Turkish rule. In 1513, in order to suppress the Venetian influence and strengthen his own authority, the sultan made a decision on separating the former vilayet of Crnojević from the composition of the Skadar sanjak, after which a separate Sanjak of Montenegro was created in that area. Skender Crnojević , the youngest brother of the last Zeta lord Đurđ Crnojević, was appointed as the first (and only) sandjakbeg.

Sandžak, also known as Sanjak, is a historical geo-political region in Serbia and Montenegro. The name Sandžak derives from the Sanjak of Novi Pazar, a former Ottoman administrative district founded in 1865. Serbs usually refer to the region by its medieval name of Raška. Between 1878 and 1909 the region was placed under Austro-Hungarian occupation, following which it was ceded back to the Ottoman Empire. In 1912 the region was divided between the kingdoms of Montenegro and Serbia. The most populous city in the region is Novi Pazar in Serbia.

The greater part of the Zetan principality lost its status as an independent state, becoming a vassal state of the Ottoman Empire, until it was added to the Ottoman administrative unit of Sanjak of Scutari in 1499. In 1514 this territory was separated from the Sanjak of Scutari and established as a separate Sanjak of Montenegro, under the rule of Skenderbeg Crnojević.

In 1523, the resm-i filori of Montenegro (Karadağ), which had the status of hass, was made up of 33 akçe in poll-tax, a 20 akçe İspençe and 2 akçe for the collector. When Skenderbeg Crnojević died in 1528, the Sanjak of Montenegro was joined to the Sanjak of Scutari, as a unique administrative unit with certain degree of autonomy.

The Prince-Bishopric of Montenegro (Serbian: Митрополство Црногорско, romanized: Mitropolstvo Crnogorsko) was an ecclesiastical principality that existed from 1516 until 1852. The principality was located around modern-day Montenegro. It emerged from the Eparchy of Cetinje, later known as the Metropolitanate of Montenegro and the Littoral, whose bishops defied the Ottoman Empire overlordship and transformed the parish of Cetinje into a de facto theocracy, ruling it as Metropolitans (Vladike, also known as prince-bishops).

The first prince-bishop was Vavila. The system was transformed into a hereditary one by Danilo Šćepčević, a bishop of Cetinje who united the several tribes of Montenegro into fighting the Ottoman Empire that had occupied all of Montenegro (as the Sanjak of Montenegro and Montenegro Vilayet) and most of southeastern Europe at the time. Danilo was the first in the House of Petrović-Njegoš to occupy the position as the Metropolitan of Cetinje in 1851, when Montenegro became a secular state (principality) under Danilo I Petrović-Njegoš. The Prince-Bishopric of Montenegro also briefly became a monarchy when it was temporarily abolished in 1767–1773: this happened when the impostor Little Stephen posed as the Russian Emperor and crowned himself the Tsar of Montenegro.

The 1582–83 census registered that the vilayet, an autonomous part of the frontier of the Sanjak of Scutari, had the nahiyah of Grbavci (13 villages), Župa (11 villages), Malonšići (7 villages), Pješivci (14 villages), Cetinje (16 villages), Rijeka (31 villages), Crmnica (11 villages), Paštrovići (36 villages) and Grbalj (9 villages); a total of 148 villages.

The Montenegrin tribes, with support of the Serbian Orthodox Eparchy of Cetinje, fought guerilla wars against the Ottomans with some degree of success. Although the Ottomans continued to nominally rule the country, the mountains were said to have never been completely conquered. There existed tribal assemblies (zbor). The head bishop (and tribal leaders) often allied themselves with the Republic of Venice. The Montenegrins fought and won two important battles at Lješkopolje, in 1604 and 1613, under the leadership and command of Metropolitan Rufim Njeguš. This was the first battle, of many, that a bishop had led, and managed to defeat the Ottomans.

During the Great Turkish War, in 1685, Suleiman, Pasha of Scutari, led a contingent that approached Cetinje, and on the way clashed with hajduks in Venetian service under the command of Bajo Pivljanin at the hill of Vrtijeljka (in the Battle of Vrtijeljka), where they annihilated the hajduks. Afterwards, the victorious Ottomans paraded with 500 severed heads through Cetinje, and also attacked the Cetinje monastery and the palace of Ivan Crnojević. The Montenegrins expelled the Ottomans and asserted independence after the Great Turkish War (1683–1699).

The Serb uprising of 1596–1597, also known as the Herzegovina uprising of 1596–1597, was a rebellion organized by Serbian Patriarch Jovan Kantul (s. 1592–1614) and led by Grdan, the vojvoda ("duke") of Nikšić against the Ottomans in the Sanjak of Herzegovina and Montenegro Vilayet, during the Long Turkish War (1593–1606). The uprising broke out in the aftermath of the failed Banat Uprising in 1594 and the burning of Saint Sava's relics on 27 April 1595; it included the tribes of Bjelopavlići, Drobnjaci, Nikšić, and Piva. The rebels, defeated at the field of Gacko (Gatačko Polje) in 1597, were forced to capitulate due to a lack of foreign support.

After the failure of the uprising, many Herzegovinians moved to the Bay of Kotor and Dalmatia. The earliest more significant Serb migrations took place between 1597 and 1600. Grdan and Patriarch Jovan would continue to plan revolts against the Ottomans in the coming years. Jovan contacted the pope again in 1599, without success. Serbian, Greek, Bulgarian, and Albanian monks visited European courts to solicit help. The first decade of the 17th century saw some successful Montenegrin battles against the Ottomans under Metropolitan Rufim. The tribe of Drobnjaci defeated the Ottomans in Gornja Bukovica on 6 May 1605. However, Ottomans retaliated the same summer and captured the duke Ivan Kaluđerović, who was eventually taken to Pljevlja and executed. From the assembly in Kosijerevo monastery, on 18 February 1608, Serb leaders urged the Spanish and Neapolitan court for final energetic action. Preoccupied, Spain could not do much in Eastern Europe. However, the Spanish fleet did attack Durrës in 1606. Finally, on 13 December 1608, Patriarch Jovan Kantul organized an assembly in Morača Monastery, gathering all the rebel leaders of Montenegro and Herzegovina. The 1596–97 uprising would stand as a model for multiple anti-Ottoman uprisings in Bosnia and Herzegovina in the coming centuries.

During the reign of Danilo two important changes occurred in the wider European context of Montenegro: the expansion of the Ottoman state was gradually reversed, and Montenegro found in the Russian Empire a powerful new patron to replace the declining Venice. The replacement of Venice by Russia was especially significant, since it brought financial aid (after Danilo visited Peter the Great in 1715), modest territorial gain, and, in 1789, formal recognition by the Ottoman Porte of Montenegro's independence as a state under Petar I Petrović Njegoš.

After Šćepan's death, gubernadur (title created by Metropolitan Danilo to appease Venetians) Jovan Radonjić, with Venetian and Austrian help, tried to impose himself as the new ruler. However, after the death of Sava (1781), the Montenegrin chiefs chose archimandrite Petar Petrović, who was a nephew of Metropolitan Vasilije, as successor.

Petar I assumed the leadership of Montenegro at a very young age and during most difficult times. He ruled almost half a century, from 1782 to 1830. Petar I won many crucial victories against the Ottomans, including at Martinići and Krusi in 1796. With these victories, Petar I liberated and consolidated control over the Highlands (Brda) that had been the focus of constant warfare, and also strengthened bonds with the Bay of Kotor, and consequently the aim to expand into the southern Adriatic coast.

In 1806, as French Emperor Napoleon advanced toward the Bay of Kotor, Montenegro, aided by several Russian battalions and a fleet of Dmitry Senyavin, went to war against the invading French forces. Undefeated in Europe, Napoleon's army was however forced to withdraw after defeats at Cavtat and at Herceg-Novi. In 1807, the Russian–French treaty ceded the Bay to France. The peace lasted less than seven years; in 1813, the Montenegrin army, with ammunition support from Russia and Britain, liberated the Bay from the French. An assembly held in Dobrota resolved to unite the Bay of Kotor with Montenegro. But at the Congress of Vienna, with Russian consent, the Bay was instead granted to Austria. In 1820, to the north of Montenegro, the Morača tribe won a major battle against an Ottoman force from Bosnia.

During his long rule, Petar strengthened the state by uniting the often quarreling tribes, consolidating his control over Montenegrin lands, and introducing the first laws in Montenegro. He had unquestioned moral authority strengthened by his military successes. His rule prepared Montenegro for the subsequent introduction of modern institutions of the state: taxes, schools and larger commercial enterprises. When he died, he was by popular sentiment proclaimed a saint.

Following the death of Petar I, his 17-year-old nephew, Rade Petrović, became Metropolitan Petar II. By historical and literary consensus, Petar II, commonly called "Njegoš", was the most impressive of the prince-bishops, having laid the foundation of the modern Montenegrin state and the subsequent Kingdom of Montenegro. He was also an acclaimed Montenegrin poet.

A long rivalry had existed between the Montenegrin metropolitans from the Petrović family and the Radonjić family, a leading clan which had long vied for power against the Petrović's authority. This rivalry culminated in Petar II's era, though he came out victorious from this challenge and strengthened his grip on power by expelling many members of the Radonjić family from Montenegro.

In domestic affairs, Petar II was a reformer. He introduced the first taxes in 1833 against stiff opposition from many Montenegrins whose strong sense of individual and tribal freedom was fundamentally in conflict with the notion of mandatory payments to the central authority. He created a formal central government consisting of three bodies, the Senate, the Guardia and the Perjaniks. The Senate consisted of 12 representatives from the most influential Montenegrin families and performed executive and judicial as well as legislative functions of government. The 32-member Guardia traveled through the country as agents of the Senate, adjudicating disputes and otherwise administering law and order. The Perjaniks were a police force, reporting both to the Senate and directly to the Metropolitan.

Before his death in 1851, Petar II named his nephew Danilo as his successor. He assigned him a tutor and sent him to Vienna, from where he continued his education in Russia. According to some historians Petar II most likely prepared Danilo to be a secular leader. However, when Petar II died, the Senate, under influence of Djordjije Petrović (the wealthiest Montenegrin at the time), proclaimed Petar II's elder brother Pero as Prince and not Metropolitan. Nevertheless, in a brief struggle for power, Pero, who commanded the support of the Senate, lost to the much younger Danilo who had more support among the people. In 1852, Danilo proclaimed a secular Principality of Montenegro with himself as Prince and formally abolished ecclesiastical rule.

Petar Petrović Njegoš, an influential vladika, reigned in the first half of the 19th century. In 1851 Danilo Petrović Njegoš became vladika, but in 1852 he married and renounced his ecclesiastical character, assuming the title of knjaz (Prince) Danilo I, and transformed his land into a secular principality. Following the assassination of Danilo by Todor Kadić in Kotor, in 1860, the Montenegrins proclaimed Nicholas I as his successor on August 14 of that year. In 1861–1862, Nicholas engaged in an unsuccessful war against the Ottoman Empire. Under Nicholas I the country was also granted its first constitution (1905) and was elevated to the rank of kingdom in 1910.

Following the Herzegovinian Uprising, partly initiated by his clandestine activities, he yet again declared war on Turkey. The Serbia joined Montenegro, but it was defeated by Turkish forces that same year. Russia now joined in and decisively routed the Turks in 1877–78. The Treaty of San Stefano (March 1878) was highly advantageous to Montenegro, as well as Russia, Serbia, Romania and Bulgaria. However, the gains were somewhat trimmed by the Treaty of Berlin (1878). In the end Montenegro was internationally recognized as an independent state, its territory was effectively doubled by the addition of 4,900 square kilometres (1,900 sq mi), the port of Bar and all the waters of Montenegro were closed to warships of all nations; and the administration of the maritime and sanitary police on the coast was placed in the hands of Austria.

The Montenegrin–Ottoman War, also known in Montenegro as the Great War, was fought between the Principality of Montenegro and the Ottoman Empire between 1876 and 1878. The war ended with Montenegrin victory and Ottoman defeat in the larger Russo-Turkish War of 1877–1878. Six major and 27 smaller battles were fought, among which was the crucial Battle of Vučji Do.

A rebellion in nearby Herzegovina sparked a series of rebellions and uprisings against the Ottomans in Europe. Montenegro and Serbia agreed to declare a war on the Ottomans on 18 June 1876. The Montenegrins allied themselves with Herzegovians. One battle that was crucial to Montenegro's victory in the war was the Battle of Vučji Do. In 1877, Montenegrins fought heavy battles along the borders of Herzegovina and Albania. Prince Nicholas took the initiative and counterattacked the Ottoman forces that were coming from the north, south and west. He conquered Nikšić (24 September 1877), Bar (10 January 1878), Ulcinj (20 January 1878), Grmožur (26 January 1878) and Vranjina and Lesendro (30 January 1878).

The war ended when the Ottomans signed a truce with the Montenegrins at Edirne on 13 January 1878. The advancement of Russian forces toward the Ottomans forced the Ottomans to sign a peace treaty on 3 March 1878, recognising the independence of Montenegro, as well as Romania and Serbia, and also increased Montenegro's territory from 4,405 km² to 9,475 km². Montenegro also gained the towns of Nikšić, Kolašin, Spuž, Podgorica, Žabljak, Bar, as well as access to the sea.

The Battle of Vučji Do was a major battle of the Montenegrin-Ottoman War of 1876-78 that took place on 18 July 1876 in Vučji Do, Montenegro, fought between the combined forces of Montenegrin and Eastern Herzegovinian tribes (battalions) against the Ottoman Army under Grand Vizier Ahmed Muhtar Pasha. The Montenegrin-Herzegovinian forces heavily defeated the Ottomans, and managed to capture two of their commanders. In addition, they captured a large consignment of armament.

The Congress of Berlin (13 June – 13 July 1878) was a diplomatic conference to reorganise the states in the Balkan Peninsula after the Russo-Turkish War of 1877–78, which had been won by Russia against the Ottoman Empire. Represented at the meeting were Europe's then six great powers (Russia, Great Britain, France, Austria-Hungary, Italy and Germany), the Ottomans and four Balkan states: Greece, Serbia, Romania and Montenegro.

The leader of the congress, German Chancellor Otto von Bismarck, sought to stabilise the Balkans, reduce the role of the defeated Ottoman Empire in the region, and balance the distinct interests of Britain, Russia and Austria-Hungary. The affected territories were instead granted varying degrees of independence. Romania became fully independent, though was forced to give part of Bessarabia to Russia, and gained Northern Dobruja. Serbia and Montenegro were also granted full independence but lost territory, with Austria-Hungary occupying the Sandžak region along with Bosnia and Herzegovina.

The First Balkan War lasted from October 1912 to May 1913 and involved actions of the Balkan League (the Kingdoms of Bulgaria, Serbia, Greece and Montenegro) against the Ottoman Empire. The Balkan states' combined armies overcame the initially numerically inferior (significantly superior by the end of the conflict) and strategically disadvantaged Ottoman armies, achieving rapid success.

The war was a comprehensive and unmitigated disaster for the Ottomans, who lost 83% of their European territories and 69% of their European population. As a result of the war, the League captured and partitioned almost all of the Ottoman Empire's remaining territories in Europe. Ensuing events also led to the creation of an independent Albania, which angered the Serbs. Bulgaria, meanwhile, was dissatisfied over the division of the spoils in Macedonia, and attacked its former allies, Serbia and Greece, on 16 June 1913 which provoked the start of the Second Balkan War.

The Second Balkan War was a conflict which broke out when Bulgaria, dissatisfied with its share of the spoils of the First Balkan War, attacked its former allies, Serbia and Greece. Serbian and Greek armies repulsed the Bulgarian offensive and counter-attacked, entering Bulgaria. With Bulgaria also having previously engaged in territorial disputes with Romania and the bulk of Bulgarian forces engaged in the south, the prospect of an easy victory incited Romanian intervention against Bulgaria. The Ottoman Empire also took advantage of the situation to regain some lost territories from the previous war. When Romanian troops approached the capital Sofia, Bulgaria asked for an armistice, resulting in the Treaty of Bucharest, in which Bulgaria had to cede portions of its First Balkan War gains to Serbia, Greece and Romania. In the Treaty of Constantinople, it lost Adrianople to the Ottomans.

Montenegro suffered severely in World War I. Shortly after Austria-Hungary declared war on Serbia (28 July 1914), Montenegro lost little time in declaring war on the Central Powers – on Austria-Hungary in the first instance – on 6 August 1914, despite Austrian diplomacy promising to cede Shkoder to Montenegro if it remained neutral. For purposes of coordination in the fight against the enemy army, Serbian General Bozidar Jankovic was named head of High Command of both Serbian and Montenegrin armies. Montenegro received 30 artillery pieces and financial help of 17 million dinars from Serbia. France contributed a colonial detachment of 200 men located in Cetinje at the beginning of war, as well as two radio-stations – located on top of Mount Lovćen and in Podgorica. Until 1915 France supplied Montenegro with necessary war material and food through the port of Bar, which was blockaded by Austrian battleships and submarines. In 1915 Italy took over this role, running supplies unsuccessfully and irregularly across the line Shengjin-Bojana-Lake Skadar, an unsecured route because of constant attacks by Albanian irregulars organised by Austrian agents. Lack of vital materials eventually led Montenegro to surrender.

Austria-Hungary dispatched a separate army to invade Montenegro and to prevent a junction of the Serbian and Montenegrin armies. This force, however, was repulsed, and from the top of the strongly fortified Lovćen, the Montenegrins carried on the bombardment of Kotor held by the enemy. The Austro-Hungarian army managed to capture the town of Pljevlja while on the other hand the Montenegrins took Budva, then under Austrian control. The Serbian victory at the Battle of Cer (15–24 August 1914) diverted enemy forces from Sandjak, and Pljevlja came into Montenegrin hands again. On August 10, 1914, the Montenegrin infantry delivered a strong attack against the Austrian garrisons, but they did not succeed in making good the advantage they first gained. They successfully resisted the Austrians in the second invasion of Serbia (September 1914) and almost succeeded in seizing Sarajevo. With the beginning of the third Austro-Hungarian invasion, however, the Montenegrin army had to retire before greatly superior numbers, and Austro-Hungarian, Bulgarian and German armies finally overran Serbia (December 1915). However, the Serbian army survived, and led by King Peter I of Serbia, started retreating across Albania. In order to support the Serbian retreat, the Montenegrin army, led by Janko Vukotic, engaged in the Battle of Mojkovac (6–7 January 1916). Montenegro also suffered a large scale invasion (January 1916) and for the remainder of the war remained in the possession of the Central Powers. See Serbian Campaign (World War I) for details. The Austrian officer Viktor Weber Edler von Webenau served as the military governor of Montenegro between 1916 and 1917. Afterwards Heinrich Clam-Martinic filled this position.

King Nicholas fled to Italy (January 1916) and then to France; the government transferred its operations to Bordeaux. Eventually the Allies liberated Montenegro from the Austrians. A newly convened National Assembly of Podgorica, accused the King of seeking a separate peace with the enemy and consequently deposed him, banned his return and decided that Montenegro should join the Kingdom of Serbia on December 1, 1918. A part of the former Montenegrin military forces still loyal to the King started a rebellion against the amalgamation, the Christmas Uprising (7 January 1919).

The Kingdom of Yugoslavia was a state in Southeast and Central Europe that existed from 1918 until 1941. From 1918 to 1929, it was officially called the Kingdom of Serbs, Croats and Slovenes, but the term "Yugoslavia" (literally "Land of South Slavs") was its colloquial name due to its origins. The official name of the state was changed to "Kingdom of Yugoslavia" by King Alexander I on 3 October 1929. The new kingdom was made up of the formerly independent kingdoms of Serbia and Montenegro (Montenegro having been absorbed into Serbia the previous month), and of a substantial amount of territory that was formerly part of Austria-Hungary, the State of Slovenes, Croats and Serbs. The main states which formed the new Kingdom were the State of Slovenes, Croats and Serbs; Vojvodina; and the Kingdom of Serbia with the Kingdom of Montenegro.

The Christmas Uprising was a failed uprising in Montenegro led by the Greens in early January 1919. The military leader of the uprising was Krsto Popović and its political leader was Jovan Plamenac. The catalyst for the uprising was the decision of the controversial Great National Assembly of the Serb People in Montenegro, commonly known as the Podgorica Assembly. The assembly decided to directly unify the Kingdom of Montenegro with the Kingdom of Serbia, which would shortly after become the Kingdom of Yugoslavia. Following a questionable candidate selection process, the unionist Whites outnumbered the Greens, who were in favour of preserving Montenegrin statehood and unification in a confederal Yugoslavia.

The uprising reached a climax in Cetinje on 7 January 1919, which was the date of Eastern Orthodox Christmas. The unionists with support from the Serbian Army defeated the rebel Greens. In the aftermath of the uprising, the dethroned King Nikola of Montenegro was forced to issue a call for peace, since many homes were destroyed. As a result of the uprising, a number of participants complicit in the uprising were tried and imprisoned. Other participants in the uprising fled to the Kingdom of Italy, meanwhile some retreated to the mountains and continued guerrilla resistance under the banner of the Montenegrin Army in exile, which lasted until 1929. The most notable guerilla militia leader was Savo Raspopović.

During World War II, Italy under Benito Mussolini occupied Montenegro in 1941 and annexed to the Kingdom of Italy the area of Kotor (Cattaro), where there was a small Venetian speaking population.

The puppet Kingdom of Montenegro was created under fascist control while Krsto Zrnov Popović returned from his exile in Rome in 1941 to attempt to lead the Zelenaši ("Green" party), who supported the reinstatement of the Montenegrin monarchy. This militia was called the Lovćen Brigade. Montenegro was ravaged by a terrible guerrilla war, mainly after Nazi Germany replaced the defeated Italians in September 1943.

During World War II, as was the case in many other parts of Yugoslavia, Montenegro was involved in some sort of civil war. Besides Montenegrin Greens, the two main factions were the Chetnik Yugoslav army, who swore allegiance to the government in exile and consisted mainly of Montenegrins who declared themselves as Serbs (many of its members were Montenegrin Whites) and Yugoslav Partisans, whose aim was the creation of a Socialist Yugoslavia after the war. Since both factions shared some similarities in their goals, particularly those relating to a unified Yugoslavia and anti-Axis resistance, the two sides joined hands and in 1941 started the 13th July uprising, the first organised uprising in occupied Europe. This occurred just two months after Yugoslavia capitulated, and liberated most of Montenegrin territory, but the rebels were unable to regain control of major towns and cities. After the failed attempts to liberate the towns of Pljevlja and Kolasin, the Italians, reinforced by Germans, recaptured all insurgent territory. At the leadership level, disagreements regarding state policy (Centralist monarchy vs. Federal Socialist republic) eventually led to a split between the two sides; they then became enemies from thereon. Constantly, both factions were trying to gain support among the population. However, eventually the Chetniks in Montenegro lost support among the population, as did other Chetnik factions within Yugoslavia. The de facto leader of the Chetniks in Montenegro, Pavle Djurisic, along with other prominent figures of the movement like Dusan Arsovic and Đorđe Lašić, were held responsible for massacres of Muslim population in eastern Bosnia and Sandzak during 1944. Their ideology of a homogeneous Serbia within Yugoslavia proved to be a major obstacle in recruiting liberals, minorities, and Montenegrins who regarded Montenegro as a nation with its own identity. These factors, in addition to the fact that some Chetniks were negotiating with the Axis, led to the Chetnik Yugoslav army losing support among the Allies in 1943. In the same year, Italy, who was until then in charge of the occupied zone, capitulated and was replaced by Germany, and the fighting continued.

Podgorica was liberated by the socialist Partisans on 19 December 1944, and the war of liberation had been won. Josip Broz Tito acknowledged Montenegro's massive contribution to the war against the Axis powers by establishing it as one of the six republics of Yugoslavia.

The Uprising in Montenegro was an uprising against Italian occupation forces in Montenegro. Initiated by the Communist Party of Yugoslavia on 13 July 1941, it was suppressed within six weeks, but continued at a much lower intensity until Battle of Pljevlja on 1 December 1941. The insurgents were led by a combination of communists and former Royal Yugoslav Army officers from Montenegro. Some of the officers had recently been released from prisoner-of-war camps following their capture during the invasion of Yugoslavia. The communists managed the organisation and provided political commissars, while the insurgent military forces were led by former officers.

Within three weeks of the start of the uprising, the insurgents managed to capture almost all the territory of Montenegro. The Italian troops were forced to retreat to their strongholds in Pljevlja, Nikšić, Cetinje and Podgorica. The counter-offensive by more than 70,000 Italian troops, commanded by General Alessandro Pirzio Biroli, was assisted by Sandžak Muslim militia and Albanian irregular forces from border areas between Montenegro and Albania, and suppressed the uprising within six weeks. Josip Broz Tito dismissed Milovan Đilas from the command of Partisan forces in Montenegro because of his mistakes during the uprising, particularly because Đilas chose a frontal struggle instead of guerrilla tactics against the Italian forces and because his "Leftist Errors". After the major defeat of 1 December 1941 during the unsuccessful attack of the communist forces on the Italian garrison in Pljevlja, many soldiers deserted Partisan forces and joined the anti-Communust Chetniks. Following this defeat, the communists terrorized the people they perceived as their enemies, which antagonized many in Montenegro. The defeat of the communist forces during the Battle of Pljevlja, combined with the policy of terror they pursued, were the main reasons for the expansion of the conflict between the communist and nationalist insurgents in Montenegro following the uprising. In the second half of December 1941, nationalist military officers Đurišić and Lašić began a mobilization of armed units separate from the Partisans.

From 1945 to 1992, Montenegro became a constituent republic of the Socialist Federal Republic of Yugoslavia; it was the smallest republic in the federation and had the lowest population. Montenegro became economically stronger than ever, since it gained help from federal funds as an under-developed Republic, and it became a tourist destination as well. After war years proved turbulent and were marked by political eliminations. Krsto Zrnov Popović, the leader of Greens was assassinated in 1947, and 10 years later, in 1957, the last Montenegrin Chetnik Vladimir Šipčić was also murdered. During this period Montenegrin Communists such as Veljko Vlahović, Svetozar Vukmanović-Tempo, Vladimir Popović and Jovo Kapicić held key positions in the federal government of Yugoslavia. In 1948 Yugoslavia faced the Tito–Stalin split, a period of high tensions between Yugoslavia and the USSR caused by disagreements about each country's influences on its neighbours, and the resolution of Informbiro. Political turmoil began within both the communist party and the nation. Pro-Soviet communists faced prosecution and imprisonment in various prisons across Yugoslavia, notably Goli Otok. Many Montenegrins, due to their traditional allegiance with Russia, declared themselves as Soviet-orientated. This political split in the communist party saw the downfall of many important communist leaders, including Montenegrins Arso Jovanović and Vlado Dapčević. Many of the people imprisoned during this period, regardless of nationality, were innocent – this was later recognised by the Yugoslav government. 1954 saw the expulsion of prominent Montenegrin politician Milovan Đilas from the communist party for criticising party leaders for forming a "new ruling class" within, Yugoslavia along with Peko Dapčević.

Through the second half of the 1940s and the whole of the 1950s, the country underwent infrastructural rejuvenation thanks to federal funding. Montenegro's historic capital Cetinje was replaced with Podgorica, which in the inter-war period became the biggest city in the Republic – although it was practically in ruins due to heavy bombing in the last stages of WW II. Podgorica had a more favorable geographical position within Montenegro, and in 1947 the seat of the Republic was moved to the city, now named Titograd in honor to Marshal Tito. Cetinje received the title of 'hero city' within Yugoslavia. Youth work actions built a railway between the two biggest cities of Titograd and Nikšić, as well as an embankment over Skadar lake linking the capital with the major port of Bar. The port of Bar was also rebuilt after being mined during the German retreat in 1944. Other ports that faced infrastructural improvement were Kotor, Risan and Tivat. In 1947 Jugopetrol Kotor was founded. Montenegro's industrialisation was demonstrated through the founding of the electronic company Obod in Cetinje, a steel mill and Trebjesa brewery in Nikšić, and the Podgorica Aluminium Plant in 1969.

The breakup of communist Yugoslavia (1991–1992) and the introduction of a multi-party political system found Montenegro with a young leadership that had risen to office only a few years earlier in the late 1980s. In effect, three men ran the republic: Milo Đukanović, Momir Bulatović and Svetozar Marović; all swept into power during the anti-bureaucratic revolution — an administrative coup of sorts within the Yugoslav Communist party, orchestrated by younger party members close to Slobodan Milošević. All three appeared devout communists on the surface, but they also had sufficient skills and adaptability to understand the dangers of clinging to traditional rigid old-guard tactics in changing times. So when the old Yugoslavia effectively ceased to exist and the multi-party political system replaced it, they quickly repackaged the Montenegrin branch of the old Communist party and renamed it the Democratic Party of Socialists of Montenegro (DPS).

During the early-to-mid-1990s Montenegro's leadership gave considerable support to Milošević's war-effort. Montenegrin reservists fought on the Dubrovnik front line, where Prime Minister Milo Đukanović visited them frequently. In April 1992, following a referendum, Montenegro decided to join Serbia in forming the Federal Republic of Yugoslavia (FRY), which officially put the Second Yugoslavia to rest.

During the 1991–1995 Bosnian War and Croatian War, Montenegro participated with its police and military forces in the attacks on Dubrovnik, Croatia and Bosnian towns along with Serbian troops, aggressive acts aimed at acquiring more territories by force, characterized by a consistent pattern of gross and systematic violations of human rights. Montenegrin General Pavle Strugar has since been convicted for his part in the bombing of Dubrovnik. Bosnian refugees were arrested by Montenegrin police and transported to Serb camps in Foča, where they were subjected to systematic torture and executed. In May 1992, the United Nations imposed an embargo on FRY: this affected many aspects of life in the country.

Due to its favourable geographical location (access to the Adriatic Sea and a water-link to Albania across Lake Skadar) Montenegro became a hub for smuggling activity. The entire Montenegrin industrial production had stopped, and the republic's main economic activity became the smuggling of user goods – especially those in short supply like petrol and cigarettes, both of which skyrocketed in price. It became a de facto legalized practice and it went on for years. At best, the Montenegrin government turned a blind eye to the illegal activity, but mostly it took an active part in it. Smuggling made millionaires out of all sorts of shady individuals, including senior government officials. Milo Đukanović continues to face actions in various Italian courts over his role in widespread smuggling during the 1990s and in providing safe haven in Montenegro for different Italian Mafia figures who also allegedly took part in the smuggling distribution chain.

The 1992 Montenegrin independence referendum was the first referendum regarding Montenegrin independence, held on 1 March 1992 in SR Montenegro, a constituent republic of the Socialist Federal Republic of Yugoslavia. The referendum was the outcome of Montenegrin President Momir Bulatović's decision to agree to the terms set by Lord Carrington which were to transform Yugoslavia into a loose association of independent states that would have the status of subjects under international law. Bulatović's decision angered his ally, the Serbian President Slobodan Milošević and the Serbian leadership, who added an amendment to the Carrington Plan that would allow states that did not wish to secede from Yugoslavia to establish a successor state. As a result of this referendum, the Federal Republic of Yugoslavia, consisting of two former constituent republics of the SFR Yugoslavia, Serbia and Montenegro, was established on 27 April 1992.

An independence referendum was held in Montenegro on 21 May 2006. It was approved by 55.5% of voters, narrowly passing the 55% threshold. By 23 May, preliminary referendum results were recognized by all five permanent members of the United Nations Security Council, suggesting widespread international recognition if Montenegro were to become formally independent. On 31 May, the referendum commission officially confirmed the results of the referendum, verifying that 55.5% of the population of Montenegrin voters had voted in favor of independence. Because voters met the controversial threshold requirement of 55% approval, the referendum was incorporated into a declaration of independence during a special parliamentary session on 31 May. The Assembly of the Republic of Montenegro made a formal Declaration of Independence on Saturday 3 June.

In response to the announcement, the government of Serbia declared itself the legal and political successor of Serbia and Montenegro, and that the government and parliament of Serbia itself would soon adopt a new constitution. The United States, China, Russia, and the institutions of the European Union all expressed their intentions to respect the referendum's results.