The Seljuks originated from the Kinik branch of the Oghuz Turks,^[1]who in the 8th century lived on the periphery of the Muslim world, north of the Caspian Sea and Aral Sea in their Oghuz Yabgu State,^[2] in the Kazakh Steppe of Turkestan. During the 10th century, Oghuz had come into close contact with Muslim cities.^[3] When Seljuk, the leader of the Seljuk clan, had a falling out with Yabghu, the supreme chieftain of the Oghuz, he split his clan off from the bulk of the Oghuz Turks and set up camp on the west bank of the lower Syr Darya.

The Seljuks migrated to Khwarezm, near the city of Jend, where they converted to Islam in 985.^[4] Khwarezm, administered by the Ma'munids, was under the nominal control of the Samanid Empire. By 999 the Samanids fell to the Kara-Khanids in Transoxiana, but the Ghaznavids occupied the lands south of the Oxus. The Seljuks became involved, having supported the last Samanid emir against the Kara-Khanids, in this power struggle in the region before establishing their own independent base.

Around 1034, Tughril and Chaghri were soundly defeated by the Oghuz Yabghu Ali Tegin and his allies, forcing them to escape from Transoxiana. Initially, Turkmens took refuge in Khwarazm, which served as one of their traditional pastures, but they were also encouraged by the local Ghaznavid governor, Harun, who hoped to utilise Seljuks for his efforts to seize Khorasan from his sovereign. When Harun was assassinated by Ghaznavid agents in 1035, they again had to flee, this time heading south across the Karakum Desert. First, Turkmens made their way to the important city of Merv, but perhaps due to its strong fortification, they then changed their route westwards to take refuge in Nasa. Finally, they arrived on the edges of Khorasan, the province considered a jewel in the Ghaznavid crown.

The Seljuks defeated the Ghaznavids at the Battle of Nasa Plains in 1035. Seljuk's grandsons, Tughril and Chaghri, received the insignias of governor, grants of land, and were given the title of dehqan.^[5]

Initially the Seljuks were repulsed by Mahmud and retired to Khwarezm, but Tughril and Chaghri led them to capture Merv and Nishapur (1037/38). Later they repeatedly raided and traded territory with his successor, Mas'ud, across Khorasan and Balkh. They begin to settle in eastern Persia.

When the Seljuq leader Tughril and his brother Chaghri began raising an army, they were seen as a threat to the Ghaznavid territories. Following the looting of border cities by Seljuq raids, Sultan Mas'ud I (son of Mahmud of Ghazni) decided to expel Seljuks from his territories.

During the march of Mas'ud's army to Sarakhs, the Seljuq raiders harassed the Ghaznavid army with hit-and-run tactics. Swift and mobile Turkmens were better fit to fight battles in the steppes and deserts than was the conservative heavily-laden army of Ghaznavid Turks. Seljuq Turkmens also destroyed the Ghaznavids' supply lines and so cut them off the nearby water wells. This seriously reduced the discipline and the morale of the Ghaznavid army. On May 23, 1040, around 16,000 Seljuk soldiers engaged in battle against a starving and demoralised Ghaznavid army in Dandanaqan and defeated them near the city of Merv destroying a large part of the Ghazanavid forces.^[6] The Seljuks occupied Nishapur, Herat, and besieged Balkh.

After the Battle of Dandanaqan, Turkmens employed Khorasanians and set up a Persian bureaucracy to administer their new polity with Toghrul as its nominal overlord. By 1046, Abbasid caliph al-Qa'im had sent Tughril a diploma recognizing Seljuk rule over Khorasan.

After the conquest of territories in present-day Iran by the Seljuk Empire, a large number of Oghuz Turks arrived on the Byzantine borderlands of Armenia in the late 1040s. Eager for plunder and distinction in the path of jihad, they began raiding the Byzantine provinces in Armenia. At the same time, the eastern defences of the Byzantine Empire had been weakened by Emperor Constantine IX Monomachos (r. 1042–1055), who allowed the thematic troops (provincial levies) of Iberia and Mesopotamia to relinquish their military obligations in favour of tax payments.

The Seljuk expansion westward was a confused affair, as it was accompanied by a mass migration of Turkish tribes. These tribes were only nominally subjects of the Seljuk rulers, and their relations were dominated by a complex dynamic: while the Seljuks aimed at establishing a state with an orderly administration, the tribes were more interested in plunder and new pasture lands, and launched raids independently of the Seljuk court. The latter tolerated this phenomenon, as it helped to defuse tensions in the Seljuk heartlands.

The Battle of Kapetron was fought between a Byzantine-Georgian army and the Seljuk Turks at the plain of Kapetron in 1048. The event was the culmination of a major raid led by the Seljuk prince Ibrahim Inal into Byzantine-ruled Armenia. A combination of factors meant that the regular Byzantine forces were at a considerable numerical disadvantage against the Turks: the local thematic armies had been disbanded, while many of the professional troops had been diverted to the Balkans to face the revolt of Leo Tornikios. As a result, the Byzantine commanders, Aaron and Katakalon Kekaumenos, disagreed on how best to confront the invasion. Kekaumenos favoured an immediate and pre-emptive strike, while Aaron favoured a more cautious strategy until the arrival of reinforcements. Emperor Constantine IX chose the latter option and ordered his forces to adopt a passive stance, while requesting aid from the Georgian ruler Liparit IV. This allowed the Turks to ravage at will, notably leading to the sack and destruction of the great commercial centre of Artze.

After the Georgians arrived, the combined Byzantine–Georgian force gave battle at Kapetron. In a fierce nocturnal battle, the Christian allies managed to repel the Turks, and Aaron and Kekaumenos, in command of the two flanks, pursued the Turks until the next morning. In the centre, however, Inal managed to capture Liparit, a fact of which the two Byzantine commanders were not informed until after they had given thanks to God for their victory. Inal was able to return unmolested to the Seljuk capital at Rayy, carrying enormous plunder. The two sides exchanged embassies, leading to the release of Liparit and the start of diplomatic relations between the Byzantine and Seljuk courts. Emperor Constantine IX took steps to strengthen his eastern frontier, but due to internal infighting the Turkish invasions did not recommence until 1054. The Turks experienced increasing success, aided by the renewed diversion of Byzantine troops to the Balkans to fight the Pechenegs, disputes between the various ethnic groups of the eastern Byzantine provinces, and the decline of the Byzantine army.

After a series of victories, Tughril conquered Baghdad, the seat of the caliphate, and ousted the last of the Buyid rulers. Tughril is declared sultan (of Great Seljuk Sultanate) by the caliph Al-Qa'im. Like the Buyids, the Seljuks kept the Abbasid caliphs as figureheads.

The founder of the Seljuk empire, Tughril, died childless and willed the throne to Alp Arslan, son of his brother Chaghri Beg. After Tughril's death however, the Seljuk prince Qutalmish hoped to become the new sultan, because Tughril was childless and he was the eldest living member of the dynasty.

Alp Arslan's main army was about 15 km east of Qutalmısh. Qutalmısh tried to change the course of a creek to block Alp Arslan's way. However Alp Arslan was able to pass his army through the newly created marsh land. Once the two Seljuk armies met, Qutalmısh's forces fled from the battle. Resul as well as Qutalmısh's son Suleyman (later founder of the Sultanate of Rum) were taken prisoner. Qutalmısh escaped, but while gathering his forces for an orderly retreat to his fort Girdkuh, he fell from his horse in a hilly terrain and died on 7 December 1063.

Although Qutalmısh's son Suleyman was taken prisoner, Alp Arslan pardoned him and sent him into exile. But later this proved to be an opportunity for him; for he founded the Sultanate of Rum, which outlasted the Great Seljuk Empire.

Arslan defeated Qutalmısh for the throne and succeeded on 27 April 1064 as sultan of the Seljuk Empire, thus becoming sole monarch of Persia from the river Oxus to the Tigris.

With the hope of capturing Caesarea Mazaca, the capital of Cappadocia, Alp Arslan placed himself at the head of the Turkoman" cavalry, crossed the Euphrates, and entered and invaded the city. Along with Nizam al-Mulk, he then marched into Armenia and Georgia, which he conquered in 1064. After a siege of 25 days, the Seljuks captured Ani, the capital city of Armenia, and slaughtered its population.

En route to fight the Fatimids in Syria in 1068, Alp Arslan invaded the Byzantine Empire. The Emperor Romanos IV Diogenes, assuming command in person, met the invaders in Cilicia. In three arduous campaigns, the Turks were defeated in detail and driven across the Euphrates in 1070. The first two campaigns were conducted by the emperor himself, while the third was directed by Manuel Comnenos, great-uncle of Emperor Manuel Comnenos.

The Battle of Manzikert was fought between the Byzantine Empire and the Seljuk Empire (led by Alp Arslan). The decisive defeat of the Byzantine army and the capture of the Emperor Romanos IV Diogenes played an important role in undermining Byzantine authority in Anatolia and Armenia, and allowed for the gradual Turkification of Anatolia. Many of the Turks, who had been travelling westward during the 11th century, saw the victory at Manzikert as an entrance to Asia Minor.

Under Alp Arslan's successor, Malik Shah, and his two Persian viziers, Nizām al-Mulk and Tāj al-Mulk, the Seljuk state expanded in various directions, to the former Iranian border of the days before the Arab invasion, so that it soon bordered China in the east and the Byzantines in the west. Malik Shāh was the one who moved the capital from Rey to Isfahan. It was under his rule and leadership that the Seljuk Empire had reached the height of its successes.

Alp Arslan authorized his Turkoman generals to carve their own principalities out of formerly Byzantine Anatolia, as atabegs loyal to him. Within two years the Turkmens had established control as far as the Aegean Sea under numerous beyliks: the Saltukids in Northeastern Anatolia, the Shah-Armens and the Mengujekids in Eastern Anatolia, Artuqids in Southeastern Anatolia, Danishmendis in Central Anatolia, Rum Seljuks (Beylik of Suleyman, which later moved to Central Anatolia) in Western Anatolia, and the Beylik of Tzachas of Smyrna in İzmir (Smyrna).

Battle of Kerj Abu Dulaf was fought in 1073 between the Seljuk Army of Malik-Shah I and Kerman Seljuk army of Qavurt and his son, Sultan-shah. It took place approximately near Kerj Abu Dulaf, the present-day between Hamadan and Arak, and was a decisive Malik-Shah I victory.

After the death of Alp-Arslan, Malik-Shah was declared as the new sultan of the empire. However, right after Malik-Shah accession, his uncle Qavurt claimed the throne for himself and sent Malik-Shah a message which said: "I am the eldest brother, and you are a youthful son; I have the greater right to my brother Alp-Arslan's inheritance." Malik-Shah then replied by sending the following message: "A brother does not inherit when there is a son.". This message enraged Qavurt, who thereafter occupied Isfahan.

In 1073 a battle took place near Hamadan, which lasted three days. Qavurt was accompanied by his seven sons, and his army consisted of Turkmens, while the army of Malik-Shah consisted of ghulams ("military slaves") and contingents of Kurdish and Arab troops.During the battle, the Turks of Malik-Shah's army mutinied against him, but he nevertheless managed to defeat and capture Qavurt. Qavurt then begged for mercy and in return promised to retire to Oman. However, Nizam al-Mulk declined the offer, claiming that sparing him was an indication of weakness. After some time, Qavurt was strangled to death with a bowstring, while two of his sons were blinded.

After a brief campaign conducted by Malik-Shah I in southern Georgia, the emperor handed the duchies of Samshvilde and Arran to a certain "Sarang of Gandza", referred to as Savthang in Arabic sources. Leaving 48,000 cavalrymen to Sarang, he ordered another campaign to bring Georgia fully under the dominion of Seljuk Empire. The ruler of Arran, aided by the Muslim rulers of Dmanisi, Dvin and Ganja marched his army into Georgia. The dating of the invasion is disputed among modern Georgian scholars. While the battle is mostly dated in 1074 (Lortkipanidze, Berdzenishvili, Papaskiri), Prof. Ivane Javakhishvili puts the time somewhere around 1073 and 1074. 19th-century Georgian historian Tedo Jordania dates the battle in 1077. According to the latest research, the battle happened either in August or in September 1075 A.D.^[7] Giorgi II, with military support of Aghsartan I of Kakheti, met the invaders near the castle of Partskhisi. Although the details of the battle remain largely unstudied, it is known that one of the most powerful Georgian nobles, Ivane Baghuashi of Kldekari, allied to the Seljuks, handing them his son, Liparit, as a political prisoner as a pledge of loyalty. The battle raged on for an entire day, finally ending with a decisive victory for Giorgi II of Georgia.^[8] The momentum gained after the victory of an important battle fought in Partskhisi allowed the Georgians to recapture all the territories lost to the Seljuk Empire (Kars, Samshvilde) as well as the Byzantine Empire (Anacopia, Klarjeti, Shavsheti, Ardahan, Javakheti).^[9]

The defeat of the Byzantine army at the Battle of Manzikert allowed the Turks, including forces loyal to Danishmend Gazi, to occupy nearly all of Anatolia. Danishmend Gazi and his forces took as their lands central Anatolia, conquering the cities of Neocaesarea, Tokat, Sivas, and Euchaita. This state controls a major route from Syria to the Byzantine Empire and this becomes a strategically important during the First Crusades.

Malik Shah I surged into Georgia and reduced many settlements to ruins. from 1079/80 onward, Georgia was pressured into submitting to Malik-Shah to ensure a precious degree of peace at the price of an annual tribute.

Suleiman ibn Qutulmish (a cousin of Melik Shah) founds Konya state in what is now west Turkey. Although a vassal of Great Seljuk Empire it soon becomes totally independent. The Sultanate of Rum seceded from the Great Seljuk Empire under Suleiman ibn Qutulmish in 1077, just six years after the Byzantine provinces of central Anatolia were conquered at the Battle of Manzikert (1071). It had its capital first at İznik and then at Konya. These Turkish groups start to disrupt the pilgrimage route going into Asia Minor.

Sultan Malik-Shah I sent his brother Tutush to Damascus to help Atsiz ibn Uvaq al-Khwarazmi, who was besieged. After the siege had ended, Tutush had Atsiz executed and installed himself in Damascus. He took over the war against the Fatimids. He may have begun to disrupt the pilgrimage trade.

Originally in Byzantine service, Tzachas, a Seljuk Turkish military commander, rebelled and seized Smyrna, much of the Aegean coastlands of Asia Minor and the islands lying off shore. He founded a principality in Smyrna, giving the Seljuks access to Aegean Sea.

In 1080, Tutush determined to capture Aleppo by force, in which he wanted to strip it from its nearby defenses; hence, he seized Manbij, Hisn al-Faya (at modern-day al-Bira), Biza'a and Azaz. He later influenced Sabiq to cede the emirate to the Uqaylid emir Muslim ibn Quraysh "Sharaf al-Dawla".

The headman in Aleppo, Sharif Hassan ibn Hibat Allah Al-Hutayti, currently under siege by Suleiman ibn Qutalmish, promised to surrender the city to Tutush. Suleiman was a distant member of the Seljuk dynasty who had established himself in Anatolia and was trying to expand his rule to Aleppo, having captured Antioch in 1084. Tutush and his army met Suleiman's forces near Aleppo in 1086. In the ensuing battle Suleiman's forces fled, Suleiman was killed and his son Kilic Arslan captured. Tutush attacked and occupied Aleppo except for the citadel in May 1086, he stayed until October and left for Damascus due to the advance of Malik-Shah's armies. The Sultan himself arrived in December 1086, then he appointed Aq Sunqur al-Hajib as the governor of Aleppo.

In the spring of 1087, news reached the Byzantine court of a huge invasion from the north. The invaders were Pechenegs from the north-west Black Sea region; it was reported that they numbered 80,000 men in all. Taking advantage of the precarious situation of the Byzantines, the Pecheneg horde headed towards the Byzantine capital at Constantinople, plundering the northern Balkans as they went. The invasion posed a serious threat to Alexios's empire, yet due to years of civil war and neglect the Byzantine military was unable to provide the emperor with enough troops to repel the Pecheneg invaders. Alexios was forced to rely on his own ingenuity and diplomatic skill to save his empire from annihilation. He appealed to another Turk nomadic tribe, the Cumans, to join him in battle against the Pechenegs. Around 1090 or 1091, Emir Chaka of Smyrna suggested an alliance with the Pechenegs in order to completely destroy the Byzantine Empire.^[10]

Won over by Alexios's offer of gold in return for aid against the Pechenegs, the Cumans hurried to join Alexios and his army. In the late spring of 1091, the Cuman forces arrived in Byzantine territory, and the combined army prepared to advance against the Pechenegs. On Monday, April 28, 1091, Alexios and his allies reached the Pecheneg camp at Levounion near the Hebros River.

The Pechenegs appear to have been caught by surprise. At any rate, the battle that took place on the next morning at Levounion was practically a massacre. The Pecheneg warriors had brought their women and children with them, and they were totally unprepared for the ferocity of the attack that was unleashed upon them. The Cumans and the Byzantines fell upon the enemy camp, slaughtering all in their path. The Pechenegs quickly collapsed, and the victorious allies butchered them so savagely that they were almost wiped out. The survivors were captured by the Byzantines and taken into imperial service.

Levounion was the single most decisive victory achieved by a Byzantine army for more than half a century. The battle marks a turning point in Byzantine history; the empire had reached the nadir of its fortunes in the last twenty years, and Levounion signalled to the world that now at last the empire was on the road to recovery. The Pechenegs had been utterly destroyed, and the empire's European possessions were now secure. Alexios had proved himself as the saviour of Byzantium in its hour of need, and a new spirit of hope began to arise in the war-weary Byzantines.

Malik-Shah died on 19 November 1092 while he was hunting. Upon his death, the Seljuk Empire fell into chaos, as rival successors and regional governors carved up their empire and waged war against each other. The individual tribes, the Danishmends, Mangujekids, Saltuqids, Tengribirmish begs, Artuqids (Ortoqids) and Akhlat-Shahs, had started vying with each other to establish their own independent states. Malik Shāh I was succeeded in Anatolia by Kilij Arslan I, who founded the Sultanate of Rum, and in Syria by his brother Tutush I. In Persia he was succeeded by his son Mahmud I, whose reign was contested by his other three brothers Barkiyaruq in Iraq, Muhammad I in Baghdad, and Ahmad Sanjar in Khorasan. The situation within the Seljuk lands was further complicated by the beginning of the First Crusade, which detached large portions of Syria and Palestine from Muslim control in 1098 and 1099. The success of the First Crusade is at least in part attributable to the political confusion which resulted from Malik-Shah's death

The armies of Tutush (along with his general the Kakuyid Ali ibn Faramurz) and Berk-Yaruq met outside Ray on 17 Safar 488 (26 February 1095 CE), but most of Tutush's allies deserted him before battle commenced, and he was killed by a ghulam (soldier-slave) of a former ally, Aq-Sonqur. Tutush was decapitated and his head was displayed in Baghdad. Tutush's younger son Duqaq then inherited Damascus, whilst Radwan received Aleppo, splitting their father's realm. Turkish power fragments just before the First Crusades.

During the First Crusade, the fractured states of the Seljuks were generally more concerned with consolidating their own territories and gaining control of their neighbours than with cooperating against the crusaders. The Seljuks easily defeated the People's Crusade arriving in 1096, but they could not stop the progress of the army of the subsequent Princes' Crusade, which took important cities such as Nicaea (İznik), Iconium (Konya), Caesarea Mazaca (Kayseri), and Antioch (Antakya) on its march to Jerusalem (Al-Quds). In 1099 the crusaders finally captured the Holy Land and set up the first Crusader states. The Seljuks had already lost Palestine to the Fatimids, who had recaptured it just before its capture by the crusaders.

The Siege of Xerigordos in 1096, Germans of the People's Crusade under Reinald against the Turks commanded by Elchanes, general of Kilij Arslan I, the Seljuk Sultan of Rûm. The crusader raiding party captured the Turkish fort of Xerigordos, about four days' march from Nicaea, in an attempt to set up a pillaging outpost. Elchanes arrived three days later and besieged the crusaders. The defenders had no water supply, and after eight days of siege, they surrendered on September 29. Some of the crusaders converted to Islam, while others who refused were killed.

In 1098, when Kerbogha heard that the Crusaders had besieged Antioch, he gathered his troops and marched to relieve the city. On his way, he attempted to regain Edessa following its recent conquest by Baldwin I, so as not to leave any Frankish garrisons behind him on his way to Antioch. For three weeks he pointlessly besieged the city before deciding to continue on to Antioch. His reinforcements could have perhaps ended the Crusade before the walls of Antioch, and, indeed, the whole Crusade was perhaps saved by his time wasted at Edessa. By the time he arrived, around June 7, the Crusaders had already won the siege, and had held the city since 3 June. They were not able to restock the city before Kerbogha, in turn, began besieging the city.

On 28 June, when Bohemond, the leader of the Christian army, decided to attack, the Emirs decided to humble Kerbogha by abandoning him at the critical moment. Kerbogha was taken by surprise by the organization and discipline of the Christian army. This motivated, unified Christian army was in fact so large that Kerbogha's strategy of dividing his own forces was ineffective. He was quickly routed by the Crusaders. He was forced to retreat, and returned to Mosul a broken man.

The Battle of Mersivan was fought between the European Crusaders and the Seljuk Turks led by Kilij Arslan I in Northern Anatolia during the Crusade of 1101. The Turks decisively defeated the Crusaders who lost an estimated four-fifths of their army near the mountains of Paphlagonia at Mersivan.

The Crusaders were organized into five divisions: the Burgundians, Raymond IV, Count of Toulouse and the Byzantines, the Germans, the French, and the Lombards. The land was well-suited to the Turks—dry and inhospitable for their enemy, it was open, with plenty of space for their cavalry units. The Turks had been troublesome to the Latins for some days, at last making certain that they went where Kilij Arslan I wanted them to be and making sure that they only found a small amount of supplies.

The battle took place over several days. On the first day, the Turks cut off the crusading armies’ advances and surrounded them. The next day, Conrad led his Germans in a raid that failed miserably. Not only did they fail to open the Turkish lines, they were unable to return to the main crusader army and had to take refuge in a nearby stronghold. This meant that they were cut off from supplies, aid, and communication for an attack that may have taken place had the Germans been able to provide their own military strength.

The third day was somewhat quiet, with little or no serious fighting taking place, but on the fourth day, the crusaders made an intensive effort to free themselves from the trap that they were in. The crusaders inflicted heavy losses on the Turks, but the attack was a failure by the end of the day. Kilij Arslan was joined by Ridwan of Aleppo and other powerful Danishmend princes.

The Lombards, in the vanguard, were defeated, the Pechenegs deserted, and the French and Germans were also forced to fall back. Raymond was trapped on a rock and was rescued by Stephen and Conrad, constable of Henry IV, Holy Roman Emperor. The battle continued into the next day, when the crusader camp was captured and the knights fled, leaving women, children, and priests behind to be killed or enslaved. Most of the Lombards, who had no horses, were soon found and killed or enslaved by the Turks. Raymond, Stephen, Count of Blois, and Stephen I, Count of Burgundy fled north to Sinope, and returned to Constantinople by ship.^[11]

The Kingdom of Kakheti-Hereti had been a tributary to the Great Seljuq Empire since the 1080s. However, in the 1104, the energetic Georgian king David IV was able to exploit internal unrest in the Seljuq state and successfully campaigned against Seljuk vassal state Kakheti-Hereti, finally turning it into one of his Saeristavo. The king of Kakheti-Hereti, Agsartan II, was captured by the Georgian nobles Baramisdze and Arshiani and was imprisoned in Kutaisi.

The Seljuk Sultan Barkiyaruq sent a large army to Georgia to retake Kakheti and Hereti. The battle was fought in southeastern part of the Kingdom, near the Ertsukhi. King David of Georgia personally took part in the battle, where the Seljuks were decisively defeated.

The Kingdom of Kakheti-Hereti had been a tributary to the Seljuk Empire since the 1080s. However, in the 1104, the energetic Georgian king David IV (c. 1089-1125) was able to exploit internal unrest in the Seljuk state and successfully campaigned against the Seljuk vassal state Kakheti-Hereti, finally turning it into one of his Saeristavo. The king of Kakheti-Hereti, Agsartan II, was captured by the Georgian nobles Baramisdze and Arshiani and was imprisoned in Kutaisi.

The Seljuk Sultan Berkyaruq sent a large army to Georgia to retake Kakheti and Hereti. The battle was fought in southeastern part of the Kingdom, in the village of Ertsukhi located in the plains southeast of Tbilisi. King David of Georgia personally took part in the battle, where the Seljuks decisively defeated the Georgians causing their army to flee. The Seljuk Turks then turned the Emirate of Tbilisi once again into one of their vassals.

The death of Mas'ud III of Ghazni in 1115 began a heated contest for the throne. Shirzad took the throne that year but the next year he was assassinated by his younger brother Arslan. Arslan had to face the rebellion of his other brother, Bahram, who received support from the Seljuk Sultan Ahmad Sanjar. Ahmad Sanjar invading from Khorasan took his army into Afghanistan and inflicted a crushing defeat to Arslan near Ghazni at Shahrabad. Arslan managed to escape and Bahram succeeded to the throne as the Seljuk's vassal.

The Kingdom of Georgia had been a tributary to the Great Seljuq Empire since the 1080s. However, in the 1090s, the energetic Georgian king David IV was able to exploit internal unrest in the Seljuq state and the success of the Western European First Crusade against Muslim control of the Holy Land, and established a relatively strong monarchy, reorganizing his army and recruiting Kipchak, Alan, and even Frankish mercenaries to lead them to the reconquest of lost lands and the expulsion of Turkish raiders. David's battles were not, like those of the Crusaders, part of a religious war against Islam, but rather was a political-military effort to liberate Caucasus from the nomadic Seljuks.

Georgia having been at war for the better part of twenty years, needed to be allowed to become productive again. To strengthen his army, King David launched a major military reform in 1118–1120 and resettled several thousand Kipchaks from the northern steppes to frontier districts of Georgia. In return, the Kipchaks provided one soldier per family, allowing King David to establish a standing army in addition to his royal troops (known as Monaspa). The new army provided the king with a much-needed force to fight both external threats and internal discontent of powerful lords.

Starting in 1120, King David began an aggressive policy of expansion, penetrating as far as the Araxes river basin and the Caspian littoral, and terrorizing Muslim traders throughout the South Caucasus. By June 1121, Tbilisi had actually been under a Georgian siege, with its Muslim élite being forced into paying a heavy tribute to David IV. The resurgence of Georgians’ military energies, as well as his demands for tribute from the independent city of Tbilisi brought about a coordinated Muslim response. In 1121, Seljuk Sultan Mahmud II (c. 1118–1131) declared a holy war on Georgia.

The battle at Didgori was the culmination of the entire Georgian–Seljuk wars and led to the Georgians' reconquest of Tbilisi in 1122. Soon after that David moved the capital from Kutaisi to Tbilisi. The victory at Didgori inaugurated the medieval Georgian Golden Age.

The Khitans were people of the Liao dynasty who moved west from Northern China when the Jin dynasty invaded and destroyed the Liao dynasty in 1125. Liao remnants were led by Yelü Dashi who took the Eastern Karakhanid capital of Balasagun. In 1137, they defeated the Western Karakhanids, a vassal of the Seljuks, at Khujand, and the Karakhanid ruler Mahmud II appealed to his Seljuk overlord Ahmed Sanjar for protection.

In 1141, Sanjar with his army arrived in Samarkand. The Kara-Khitans, who were invited by the Khwarazmians (then also a vassal of the Seljuks) to conquer the lands of the Seljuks, and also responding to an appeal to intervene by the Karluks who were involved in a conflict with the Karakhanids and Seljuks, also arrived. At the Battle of Qatwan, the Seljuqs were decisively defeated, which signalled the beginning of the end of the Great Seljuk Empire.

During this time conflict with the Crusader states was also intermittent, and after the First Crusade increasingly independent atabegs would frequently ally with the Crusader states against other atabegs as they vied with each other for territory. At Mosul, Zengi succeeded Kerbogha as atabeg and successfully began the process of consolidating the atabegs of Syria. In 1144 Zengi captured Edessa, as the County of Edessa had allied itself with the Artuqids against him. This event triggered the launch of the Second Crusade. Nur ad-Din, one of Zengi's sons who succeeded him as atabeg of Aleppo, created an alliance in the region to oppose the Second Crusade, which landed in 1147.

During this time conflict with the Crusader states was also intermittent, and after the First Crusade increasingly independent atabegs would frequently ally with the Crusader states against other atabegs as they vied with each other for territory. At Mosul, Zengi succeeded Kerbogha as atabeg and successfully began the process of consolidating the atabegs of Syria. In 1144 Zengi captured Edessa, as the County of Edessa had allied itself with the Artuqids against him. This event triggered the launch of the Second Crusade. Nur ad-Din, one of Zengi's sons who succeeded him as atabeg of Aleppo, created an alliance in the region to oppose the Second Crusade, which landed in 1147.

In 1153, the Ghuzz (Oghuz Turks) rebelled and captured Sanjar. He managed to escape after three years but died a year later. The atabegs, such as the Zengids and Artuqids, were only nominally under the Seljuk Sultan, and generally controlled Syria independently. When Ahmad Sanjar died in 1157, this fractured the empire even further and rendered the atabegs effectively independent. On other fronts, the Kingdom of Georgia began to become a regional power and extended its borders at the expense of Great Seljuk. The same was true during the revival of the Armenian Kingdom of Cilicia under Leo II of Armenia in Anatolia. The Abbasid caliph An-Nasir also began to reassert the authority of the caliph and allied himself with the Khwarezmshah Takash.

For a brief period, Togrul III was the Sultan of all Seljuk except for Anatolia. In 1194, however, Togrul was defeated by Takash, the Shah of Khwarezmid Empire, and the Seljuk Empire finally collapsed. Of the former Seljuk Empire, only the Sultanate of Rûm in Anatolia remained

The Seljuks were educated in the service of Muslim courts as slaves or mercenaries. The dynasty brought revival, energy, and reunion to the Islamic civilization hitherto dominated by Arabs and Persians.

The Seljuks founded universities and were also patrons of art and literature. Their reign is characterized by Persian astronomers such as Omar Khayyám, and the Persian philosopher al-Ghazali. Under the Seljuks, New Persian became the language for historical recording, while the center of Arabic language culture shifted from Baghdad to Cairo.

As the dynasty declined in the middle of the thirteenth century, the Mongols invaded Anatolia in the 1260s and divided it into small emirates called the Anatolian beyliks. Eventually one of these, the Ottoman, would rise to power and conquer the rest.