Byzantine Empire: Nicaean–Latin Wars

The sack of Constantinople occurred in April 1204 and marked the culmination of the Fourth Crusade. It is a major turning point in medieval history. Crusader armies captured, looted, and destroyed parts of Constantinople, then the capital of the Byzantine Empire. After the capture of the city, territories were divided up among the Crusaders.

Andronikos I's grandsons, Alexios and David Komnenos conquer Trebizond with the assistance of Queen Tamar of Georgia. Alexios assumes the title of emperor, establishing a Byzantine successor state, the Empire of Trebizond, in northeastern Anatolia.

Baldwin I was the first emperor of the Latin Empire of Constantinople; Count of Flanders (as Baldwin IX) from 1194 to 1205 and Count of Hainaut (as Baldwin VI) from 1195-1205. Baldwin was one of the most prominent leaders of the Fourth Crusade, which resulted in the sack of Constantinople in 1204, the conquest of large parts of the Byzantine Empire, and the foundation of the Latin Empire. He lost his final battle to Kaloyan, the emperor of Bulgaria, and spent his last days as his prisoner.

A commission of 12 crusaders and 12 Venetians decide on the distribution of the Byzantine Empire, including territories still under the rule of Byzantine claimants. In accordance with their March pact, one-quarter of the land is assigned to the emperor, while the remaining territory is divided between the Venetians and the Latin aristocrats.

After the fall of Constantinople to the crusaders in 1204, Boniface of Montferrat, the leader of the crusade, was expected by both the Crusaders and the defeated Byzantines to become the new emperor. However, the Venetians felt that Boniface was too closely tied to the Byzantine Empire, as his brother Conrad had married into the Byzantine imperial family. The Venetians wanted an emperor whom they could control more easily, and with their influence, Baldwin of Flanders was elected as emperor of the new Latin Empire.

Boniface reluctantly accepted this, and set out to conquer Thessalonica, the second-largest Byzantine city after Constantinople. At first he had to compete with Emperor Baldwin, who also wanted the city. He then went on to capture the city later in 1204 and set up a kingdom there, subordinate to Baldwin, although the title of "king" was never officially used.

In 1204–05, Boniface was able to extend his rule south into Greece, advancing through Thessaly, Boeotia, Euboea, and Attica Boniface's rule lasted less than two years before he was ambushed by Tsar Kaloyan of Bulgaria and killed on September 4, 1207. The kingdom passed to Boniface's son Demetrius, who was still a baby, so actual power was held by various minor nobles of Lombard origin.

In 1204, Byzantine emperor Alexios V Ducas Murtzouphlos fled Constantinople after crusaders invaded the city. Soon after, Theodore I Lascaris, the son-in-law of Emperor Alexios III Angelos, was proclaimed emperor but he too, realizing the situation in Constantinople was hopeless, fled to the city of Nicaea in Bithynia.

Theodore Lascaris was not immediately successful, as Henry of Flanders defeated him at Poimanenon and Prusa (now Bursa) in 1204. But Theodore was able to capture much of northwestern Anatolia after the Bulgarian defeat of Latin Emperor Baldwin I in the Battle of Adrianople, because Henry was recalled to Europe to defend against invasions from Tsar Kaloyan of Bulgaria. Theodore also defeated an army from Trebizond, as well as other minor rivals, leaving him in charge of the most powerful of the successor states.

In 1205, he assumed the traditional titles of the Byzantine emperors. Three years later, he convoked a Church council to elect a new Orthodox patriarch of Constantinople. The new patriarch crowned Theodore emperor and established his seat at Theodore's capital, Nicaea.

The Battle of Adramyttion occurred on 19 March 1205 between the Latin Crusaders and the Byzantine Greek Empire of Nicaea, one of the kingdoms established after the fall of Constantinople to the Fourth Crusade in 1204. It resulted in a comprehensive victory for the Latins. There are two accounts of the battle, one by Geoffrey de Villehardouin, and the other by Nicetas Choniates, which differ significantly.

A Crusader force of between 500 and 700 knights and infantry under the command of William of Champlitte and Geoffrey I of Villehardouin advanced into the Morea to deal with Byzantine resistance. In the olive grove of Kountouras in Messenia, they confronted an army of around 4,000–5,000 local Greeks and Slavs under the command of a certain Michael, sometimes identified with Michael I Komnenos Doukas, the founder of the Despotate of Epirus. In the ensuing battle, the Crusaders emerged victorious, forcing the Byzantines to retreat and crushing resistance in the Morea. This battle paved the way for the foundation of the Principality of Achaea.

Around the same time, Tsar Kaloyan, the Tsar of Bulgaria, successfully completed negotiations with Pope Innocent III. The Bulgarian ruler was recognized as "rex", i.e. emperor (tsar), while the Bulgarian archbishop regained the title "primas", a title equal to that of patriarch.

Despite the apparently good relations between Tsar Kaloyan and the new Western European conquerors, immediately after settling down in Constantinopole, the Latins stated their pretensions on Bulgarian lands. Latin knights began crossing the border to pillage Bulgarian towns and villages. These belligerent actions convinced the Bulgarian Emperor that an alliance with the Latins was impossible and that it was necessary to find allies from among the Greeks of Thrace that had yet to be conquered by the knights. In the winter of 1204-1205 messengers of the local Greek aristocracy visited Kaloyan and an alliance was formed.

The Battle of Adrianople occurred around Adrianople on April 14, 1205 between Bulgarians, Vlachs and Cumans under Tsar Kaloyan of Bulgaria, and Crusaders under Baldwin I, who only months before had been crowned Emperor of Constantinople, allied with Venetians under Doge Enrico Dandolo. The battle was won by the Bulgarian Empire after a successful ambush. The main part of the Latin army is eliminated, the knights are defeated and their emperor, Baldwin I, is taken prisoner in Veliko Tarnovo.

The Epirote state was founded in 1205 by Michael Komnenos Doukas, a cousin of the Byzantine emperors Isaac II Angelos and Alexios III Angelos. At first, Michael allied with Boniface of Montferrat, but having lost the Morea (Peloponnese) to the Franks at the battle of the Olive Grove of Koundouros, he went to Epirus, where he considered himself the Byzantine governor of the old province of Nicopolis and revolted against Boniface. Epirus soon became the new home of many refugees from Constantinople, Thessaly, and the Peloponnese, and Michael was described as a second Noah, rescuing men from the Latin flood. John X Kamateros, the Patriarch of Constantinople, did not consider him a legitimate successor and instead joined Theodore I Laskaris in Nicaea; Michael instead recognized the authority of Pope Innocent III over Epirus, cutting ties to the Eastern Orthodox Church.

After the stunning victory in the battle of Adrianople (1205) the Bulgarians gained control of most of Thrace except several larger cities which Emperor Kaloyan wanted to capture. In June 1205 he moved the theatre of the military actions to the south-west towards the domains of Boniface Montferrat, the King of Thessalonica and vassal of the Latin Empire.

The first town on the way of the Bulgarian army was Serres. The Crusaders tried to fight back in the vicinity of the town, but after the dead of the commander Hugues de Coligny were defeated and had to pull back to the town but during their retreat the Bulgarian troops also entered Serres. The remaining Latins under the command of Guillaume d'Arles were besieged in the citadel. In the negotiations which followed Kaloyan agreed to give them safe conduct to the Bulgarian-Hungarian border. However, when the garrison surrendered, the knights were killed while the ordinary people were spared.

The successful campaign in 1205 ended with the capture of Philippopolis and other Thracian towns. The Byzantine nobility of the city, led by Alexios Aspietes, resisted. After Kaloyan seized the city its ramparts were destroyed and Aspietes was hanged. He orders the execution of their Greek leaders and sends thousands of captured Greeks to Bulgaria.

The Latin Empire suffered heavy casualties and in the fall of 1205 the Crusaders tried to regroup and reorganize the remains of their army. Their main forces consisted of 140 knights and several thousand soldiers based in Rusion. This army was led by Thierry de Termonde and Thierry de Looz who were among the most notable nobles of the Latin Empire of Constantinople.

The battle of Rusion occurred in the winter of 1206 near the fortress of Rusion (Rusköy contemporary Keşan) between the armies of the Bulgarian Empire and the Latin Empire of Byzantium. The Bulgarians scored a major victory.

In the whole military operation the Crusaders lost more than 200 knights, many thousands of soldiers and several Venetian garrisons were completely annihilated. The new Emperor of the Latin Empire Henry of Flanders had to ask the French King for another 600 knights and 10,000 soldiers. Geoffrey of Villehardouin compared the defeat with the disaster at Adrianople. However, the Crusaders were lucky - in 1207 Tsar Kaloyan was killed during the siege of Thessaloniki and the new Emperor Boril who was a usurper needed time to enforce his authority.

After the Bulgarians annihilated the Latin army in the battle of Rusion on 31 January 1206 the remnants of the shattered Crusader forces headed to the coastal town of Rodosto to seek refuge. The town had a strong Venetian garrison and was further supported by a regiment of 2,000 troops from Constantinople. However, the fear of the Bulgarians was so great that the Latins panicked with the very arrival of the Bulgarian soldiers. They were incapable to resist and after a short battle the Venetians began to flee to their ships in the port. In their haste to escape many boats were overloaded and sank and most Venetians drowned. The town was looted by the Bulgarians who continued their victorious march through eastern Thrace and captured many more towns and fortresses.

When his elder brother, Emperor Baldwin, was captured at the Battle of Adrianople in April 1205 by the Bulgarians, Henry was chosen regent of the empire, succeeding to the throne when the news of Baldwin's death arrived. He was crowned 20 August 1206.

Upon Henry's ascension as Latin emperor, the Lombard nobles of the Kingdom of Thessalonica refused to give him allegiance. A two-year war ensued and after defeating the Templar-supported Lombards, Henry confiscated the Templar castles of Ravennika and Zetouni (Lamia).

Henry was a wise ruler, whose reign was largely passed in successful struggles with Tsar Kaloyan of Bulgaria and with his rival Emperor Theodore I Lascaris of Nicaea. He later fought against Boril of Bulgaria (1207–1218) and managed to defeat him in the Battle of Philippopolis. Henry campaigned against the Nicean Empire, expanding a small holding in Asia Minor (at Pegai) with campaigns in 1207 (at Nicomedia) and in 1211–1212 (with the Battle of the Rhyndacus), where he captured important Nicean possessions at Nymphaion. Though Theodore I Laskaris could not oppose this later campaign, it appears that Henry decided it best to focus on his European problems, for he sought a truce with Theodore I in 1214, and amicably divided Latin from Nicean possessions to the favour of Nicea.

The Siege of Antalya was the successful Turkish capture of the city of Attalia (today Antalya, Turkey), a port in southern-western Asia Minor. The capture of port gave the Turks another path into the Mediterranean although it would be another 100 years before the Turks made any serious attempts into the sea.

The port had come under the control of a Tuscan adventurer by the name of Aldobrandini, who had been in the service of the Byzantine Empire, but reputedly mistreated Egyptian merchants at that port. The inhabitants appealed to the regent of Cyprus, Gautier de Montbeliard, who occupied the town but was unable to prevent the Seljuk Turks from ravaging the adjacent countryside. Sultan Kaykhusraw I took the town by storm in March 1207, and put his lieutenant Mubariz al-Din Ertokush ibn 'Abd Allah in charge as its governor.

The Battle of Messinopolis took place on 4 September 1207, at Mosynopolis near the town of Komotini in contemporary Greece, and was fought between the Bulgarians and the Latin Empire. It resulted in a Bulgarian victory. While the armies of the Bulgarian emperor Kaloyan were besieging Odrin, Boniface of Montferrat, king of Thessalonica, launched attacks towards Bulgaria from Serres. His cavalry reached Messinopolis at 5 days raid to the east of Serres but in the mountainous terrain around the town his army was attacked by a larger force composed mainly of local Bulgarians. The battle began in the Latin rear guard and Boniface managed to repulse the Bulgarians, but while he was chasing them he was killed by an arrow, and soon the crusaders were defeated. His head was sent to Kaloyan, who immediately organized a campaign against Boniface's capital of Thessalonica.

Fortunately for the Latin Empire, Kaloyan died during the siege of Thessalonica in October 1207 and the new Emperor Boril who was a usurper needed time to enforce his authority.

In the reign of Kaloyan, the Greek noblemen of eastern Thrace had risen up against the Bulgarian Empire, seeking assistance from the Latin Empire; this rebellion would continue against the new Emperor of Bulgaria Boril, who continued the war of his predecessor Kaloyan against the Latin Empire invaded Eastern Thrace. During his march, he seized parts of Alexius Slav's territory before stopping at Stara Zagora.

The Latin Emperor Henry gathered an army in Selymbria and headed to Adrianople. The battle of Beroia took place in June 1208 near the city of Stara Zagora, Bulgaria between the Bulgarians and the Latin Empire. It resulted in a Bulgarian victory. he retreat continued for twelve days, in which the Bulgarians closely followed and harassed their opponents inflicting casualties mainly to the Latin rear-guard which was saved several times from complete collapse by the main Crusader forces. However, near Plovdiv the Crusaders finally accepted the battle and the Bulgarians were defeated.

Boril of Bulgaria invades Thrace. Henry makes an alliance with Boril's rebellious cousin, Alexius Slav. The Latins inflict a crushing defeat on the Bulgarians at Philippopolis and capture the town. Alexius Slav swears fealty to Henry through the traditional Byzantine ceremony of proskynesis (involving a kiss on Henry's feet and hand).

Alexios III had fled Constantinople on the approach of the Crusaders in 1203, but had not given up on his rights to the throne, and was determined to reclaim it. Kaykhusraw, having found in supporting Alexios's cause a perfect pretext for attacking Nicaean territory, sent an emissary to Theodore at Nicaea, calling upon him to relinquish his domains to the legitimate emperor. Theodore refused to reply to the sultan's demands, and the sultan assembled his army and invaded Laskaris' domains.

At the Battle of Antioch on the Meander, the Seljuk sultan sought out Laskaris, who was hard pressed by the attacking Turkish troops. Kaykhusraw charged his enemy and gave him a heavy blow on the head with a mace, so that the Nicaean emperor, dizzied, fell from his horse. Kaykhusraw was already giving orders to his retinue to carry Laskaris away, when the latter regained his composure and brought Kaykhusraw down by hacking at his mount's rear legs. The sultan too fell on the ground and was beheaded. His head was impaled on a lance and hoisted aloft for his army to see, causing the Turks to panic and retreat.

In this way Laskaris snatched victory from the jaws of defeat, although his own army was well-nigh destroyed in the process. The battle ended the Seljuk threat: Kaykhusraw's son and successor, Kaykaus I, concluded a truce with Nicaea on 14 June 1211, and the border between the two states would remain virtually unchallenged until the 1260s. The former emperor Alexios III, Laskaris's father-in-law, was also captured during the battle. Laskaris treated him well but stripped him of his imperial insignia and consigned him to the monastery of Hyakinthos in Nicaea, where he ended his days.

Taking advantage of the losses suffered by the Nicaean army against the Seljuks in the Battle of Antioch on the Meander, Henry landed with his army at Pegai and marched eastward to the Rhyndacus river. Henry had probably some 260 Frankish knights. Laskaris had a larger force overall, but only a handful of Frankish mercenaries of his own, as they had suffered especially heavily against the Seljuks. Laskaris prepared an ambush at the Rhyndacus, but Henry assaulted his positions and scattered the Nicaean troops in a day-long battle on 15 October. The Latin victory, won reportedly without casualties, was crushing: after the battle Henry marched unopposed through Nicaean lands, reaching south as far as Nymphaion.

Warfare lapsed thereafter, and both sides concluded the Treaty of Nymphaeum, which gave the Latin Empire control of most of Mysia up to the village of Kalamos (modern Gelenbe), which was to be uninhabited and mark the boundary between the two states.

The Treaty of Nymphaeum was a peace treaty signed in December 1214 between the Nicaean Empire, successor state of the Byzantine Empire, and the Latin Empire. Although both sides would continue to fight for years to come, there were some important consequences of this peace agreement.

1. First, the peace treaty effectively recognized both parties, as neither one was strong enough to destroy the other.
2. The second consequence of the treaty was that David Komnenos, who had been a vassal of Henry and who had been carrying out his own war against Nicaea with the support of the Latin Empire, now effectively lost that support. Theodore was thus able to annex all of David's lands west of Sinope in late 1214, gaining access to the Black Sea.
3. The third consequence was that Theodore was now free to wage war against the Seljuqs without the distraction of the Latins for the time being. Nicaea was able to consolidate their eastern frontier for the remainder of the century.

Hostilities broke out again in 1224, and a crushing Nicaean victory at the Second Battle of Poemanenum reduced Latin territories in Asia effectively only to the Nicomedian peninsula. This treaty allowed the Nicaeans to go on the offensive in Europe years later, culminating in the reconquest of Constantinople in 1261.

The Battle of Poimanenon or Poemanenum was fought in early 1224 (or possibly late 1223) between the forces of the two main successor states of the Byzantine Empire; the Latin Empire and the Byzantine Greek Empire of Nicaea. The opposing forces met at Poimanenon, south of Cyzicus in Mysia, near Lake Kuş.

Summing up the importance of this battle, the 13th-century Byzantine historian George Akropolites wrote that "Since then (this battle), the state of the Italians [the Latin Empire] ... began to decline".

The news about the defeat at Poimanenon caused panic in the Latin imperial army besieging Serres from the Despotate of Epirus, which withdrew in chaos in the direction of Constantinople and was therefore defeated decisively by the troops of the Epirote ruler, Theodore Komnenos Doukas. This victory opened up the way for the recovery of most of the Latin possessions in Asia. Threatened both by Nicaea in Asia and Epirus in Europe, the Latin emperor sued for peace, which was concluded in 1225. According to its terms, the Latins abandoned all their Asian possessions except for the eastern shore of the Bosporus and the city of Nicomedia with the surrounding region.

After the death of the Latin emperor Robert of Courtenay in 1228, Ivan Asen II was considered the most probable choice for regent of Baldwin II. Theodore thought that Bulgaria was the only obstacle left on his way to Constantinople and in the beginning of March 1230 he invaded the country, breaking the peace treaty and without a declaration of war.

The Battle of Klokotnitsa occurred on 9 March 1230 near the village of Klokotnitsa between Second Bulgarian Empire and Empire of Thessalonica. As a result, Bulgaria emerged once again as the most powerful state in South-Eastern Europe. Nevertheless, Bulgarian power was soon to be contested and surpassed by the rising Empire of Nicaea. The Epirote threat to the Latin Empire was removed. Thessalonica itself became a Bulgarian vassal under Theodore's brother Manuel.

The siege of Constantinople (1235) was a joint Bulgarian-Nicaean siege on the capital of the Latin Empire. Latin emperor John of Brienne was besieged by the Nicaean emperor John III Doukas Vatatzes and Tsar Ivan Asen II of Bulgaria. The siege remained unsuccessful.

Mongol invasions of Anatolia occurred at various times, starting with the campaign of 1241–1243 that culminated in the Battle of Köse Dağ. Real power over Anatolia was exercised by the Mongols after the Seljuks surrendered in 1243 until the fall of the Ilkhanate in 1335. Although John III was worried they might attack him next, they ended up eliminating the Seljuk threat to Nicaea. John III prepared for the coming Mongol threat. However, he had sent envoys to the Qaghans Güyük and Möngke but was playing for time. The Mongol Empire did not cause any harm to his plan to recapture Constantinople from the hands of the Latins who also sent their envoy to the Mongols.

The Battle of Constantinople was a naval battle between the fleets of the Empire of Nicaea and the Republic of Venice that occurred in May–June 1241 near Constantinople.

During the Mongol invasion of Europe, Mongol tumens led by Batu Khan and Kadan invaded Serbia and then Bulgaria in the spring of 1242 after defeating the Hungarians at the battle of Mohi and ravaging the Hungarian regions of Croatia, Dalmatia and Bosnia. Initially, the troops of Kadan moved south along the Adriatic Sea into Serbian territory. Then, turning east, it crossed the centre of the country—plundering as it went—and entered Bulgaria, where it was joined by the rest of the army under Batu. The campaigning in Bulgaria probably happened mainly in the north, where archaeology yields evidence of destruction from this period. The Mongols did, however, cross Bulgaria to attack the Latin Empire to its south before withdrawing completely. Bulgaria was forced to pay tribute to the Mongols, and this continued thereafter.

In the summer of 1242, a Mongol force invaded the Latin Empire of Constantinople. This force, a detachment of the army under Qadan then devastating Bulgaria, entered the empire from the north. It was met by the Emperor Baldwin II, who was victorious in a first encounter but was subsequently defeated. The encounters probably took place in Thrace, but little can be said about them owing to the paucity of sources. Subsequent relations between Baldwin and the Mongol khans have been taken as evidence by some that Baldwin was captured and forced to make submission to the Mongols and pay tribute. Together with the major Mongol invasion of Anatolia the following year (1243), the Mongol defeat of Baldwin precipitated a power shift in the Aegean world.

In 1246, John III Vatatzes attacked Bulgaria and recovered most of Thrace and Macedonia, and proceeded to incorporate Thessalonica into his realm. By 1248, John had defeated the Bulgarians and surrounded the Latin Empire. He continued to take land from the Latins until his death in 1254. By 1247, the Nicaeans had effectively surrounded Constantinople, with only the city's strong walls holding them at bay.

The Genoese took possession of the city and island, a dependency of the Empire of Nicaea, in a surprise attack in 1248, and held it, with aid from the Principality of Achaea. John III Doukas Vatatzes retook Rhodes in late 1249 or early 1250 and became fully incorporated into the Empire of Nicaea.

A few days after the death of Emperor Theodore Laskaris in 1258, Michael Palaiologos instigated a coup against the influential bureaucrat George Mouzalon, seizing from him the guardianship of the eight-year-old Emperor John IV Doukas Laskaris. Michael was invested with the titles of megas doux and, on 13 November 1258, of despotēs. On 1 January 1259 Michael VIII Palaiologos was proclaimed co-emperor (basileus), most likely without John IV, in Nymphaion.

The Battle of Pelagonia or Battle of Kastoria took place in early summer or autumn 1259, between the Empire of Nicaea and an anti-Nicaean alliance comprising Despotate of Epirus, Sicily and the Principality of Achaea. It was a decisive event in the history of the Eastern Mediterranean, ensuring the eventual reconquest of Constantinople and the end of the Latin Empire in 1261.

The rising power of Nicaea in the southern Balkans, and the ambitions of its ruler, Michael VIII Palaiologos, to recover Constantinople, led the formation of a coalition between the Epirote Greeks, under Michael II Komnenos Doukas, and the chief Latin rulers of the time, the Prince of Achaea, William of Villehardouin, and Manfred of Sicily. The details of the battle, including its precise date and location, are disputed as the primary sources give contradictory information; modern scholars usually place it either in July or in September, somewhere in the plain of Pelagonia or near Kastoria. It appears that the barely concealed rivalries between the Epirote Greeks and their Latin allies came to the fore in the lead-up to the battle, possibly fanned by Palaiologos' agents. As a result, the Epirotes abandoned the Latins on the eve of the battle, while Michael II's bastard son John Doukas defected to the Nicaean camp. The Latins were then set upon by the Nicaeans and routed, while many nobles, including Villehardouin, were taken captive.

The battle cleared the last obstacle to the Nicaean reconquest of Constantinople in 1261 and the re-establishment of the Byzantine Empire under the Palaiologos dynasty. It also led to the brief conquest of Epirus and Thessaly by Nicaean forces, although Michael II and his sons rapidly managed to reverse these gains. In 1262, William of Villehardouin was released in exchange for three fortresses on the southeastern tip of the Morea peninsula.

In 1260, Michael began the assault on Constantinople itself, which his predecessors had been unable to do. He allied with Genoa, and his general Alexios Strategopoulos spent months observing Constantinople in order to plan his attack. In July 1261, as most of the Latin army was fighting elsewhere, Alexius was able to convince the guards to open the gates of the city. Once inside he burned the Venetian quarter (as Venice was an enemy of Genoa, and had been largely responsible for the capture of the city in 1204).

Michael was recognized as emperor a few weeks later, restoring the Byzantine Empire under the Palaiologos dynasty, after an interval of 57 years where the city had been the capital of the Latin Empire installed by the Fourth Crusade in 1204. Achaea was soon recaptured, but Trebizond and Epirus remained independent Byzantine Greek states. The restored empire also faced a new threat from the Ottomans, when they arose to replace the Seljuks.