41°00′30″N28°58′30″E / 41.0083°N 28.9750°E /41.0083; 28.9750
| Siege of Constantinople (1235–1236) | |||||||
|---|---|---|---|---|---|---|---|
| Part of theNicaean–Latin wars Bulgarian–Latin wars | |||||||
 Map showing Constantinople and its walls during the Byzantine era | |||||||
| |||||||
| Belligerents | |||||||
 Empire of Nicaea Bulgarian Empire |  Latin Empire Duchy of Naxos | ||||||
| Commanders and leaders | |||||||
| John III Vatatzes Ivan Asen II Manuel Doukas Michael II Komnenos Doukas | John of Brienne Angelo Sanudo Geoffrey II of Villehardouin John of Béthune | ||||||
| Strength | |||||||
| Unknown | Unknown | ||||||
| Casualties and losses | |||||||
| Unknown | Unknown | ||||||
Thesiege of Constantinople (1235–1236) was a siege on the capital of theLatin Empire under Latin EmperorJohn of Brienne by a jointBulgarian–Nicaean army led by the TsarIvan Asen II of Bulgaria and the Emperor of NicaeaJohn III Doukas Vatatzes.
Despite their combined strength against a small garrison, the siege failed to breachConstantinople's fortifications supported by theVenetian navy. The allied army withdrew in the autumn for the winter and renewed the siege in 1236. Later that year Asen shifted his allegiance, presumably to avoid calls for a crusade from the pope or because sought to capture the city himself, before ultimately abandoning the Latin Empire a year later and refraining from future campaigns. While the siege did not topple the Latin Empire, it increased pressure against Latin‐rule and foreshadowed the eventual Byzantine recovery of Constantinople in 1261 by the Nicaean forces.
TheFourth Crusade resulted in the partition ofByzantine empire's territories among the crusaders. Starting in 1204, the newly established Latin Empire struggled to consolidate their power,[1] as its authority was immediately challenged by Byzantinerump states (Nicaea andEpirus). Meanwhile, in the north, Bulgarian gathered an army aimed to control parts ofMacedonia andThrace, regions claimed by the newly established Latin Empire.[2]
The struggle for control of Macedonia and Thrace between the different regional powers, often forming and breaking agreements between them, led much destruction to cities of north Greece, such asSerres andPhilippopolis, which weakened the economic support of Constantinople. After the death ofRobert of Courtenay in 1228, John of Brienne became the new Emperor of the Latin Empire. The Epirote defeat by the Bulgarians at theBattle of Klokotnitsa (1230), renewed the communication between Nicaea and the Bulgarians for an alliance against the Latin Empire.[3]
In the spring of 1235, Varatzes crossed theDardanelles and took overGallipoli. Asen along with his family arrived there to meet with Vatatzes and his court, where they concluded an alliance for a joint campaign against the Latin Empire. Part of the agreement for the alliance was the recognition of the Bulgarian Church'sautocephaly by the Nicaean church, granting the title ofPatriarch of Bulgaria to the archbishop ofTărnovo. In return, Nicaean patriarch was recognized by Asen asecumenical and he gave up his claims overMount Athos, along with ecclesiastical authority in the areas of eastern Thrace andThessaloniki.[4] The alliance was sealed with the marriage between Asen's daughter,Elena, and the Nicean heir,Theodore. The joint campaign started the summer of the same year right after the marriage.[5][6]
The Nicaean army moved from Gallipoli north, seizing territories from Latin Empire in Thrace from the east coast up to the mouth of theMarica, including the fortress ofTzurulum located west of Constantinople. Having secured the surrounding territory, the two armies joined forces to lay siege to Constantinople.[7]
The Latin Emperor had at his command a smallgarrison, which included 160knights. The defenders were able to repel the besieging forces. The Nicaean fleet tried to penetrate the defenses of theGolden Horn but it was partially destroyed by theVenetians, who had send anaval squadron for the defense of Constantinople. The joint Bulgarian–Nicaean siege was unsuccessful and they retreated in the autumn due to the incoming winter. Asen and Vatatzes agreed to continue the siege in the following year and after the departure of the Venetian fleet.[8]
The second phase of the siege, lasting into the spring of 1236, brought no significant progress. The defenders had received assistance fromGeoffrey II Villehardouin ofMorea and the Italian republics (Venice,Genoa andPisa).[7][8]
The alliance between Asen and Vatatzes was short-lived and instead allied with the Latin Empire. Asen's army reinforced by displacedCumans from theSteppe by theMongols attacked the Nicaean possessions, including the fortress of Tzurulum.[9] Scholars have presented two plausible explanations for this action. He may had reconsidered the agreement upon realizing that Nicaea stood to gain the most. If Constantinople was captured, it would had become the center of a Greek Empire preventing in the future its capture by Bulgarians.[7] At the same time,Pope Gregory IX increased calls for a crusade against him, particularly urgingHungary to attack from the north, because Asen refused to accept union with theChurch of Rome and instead he allied withschismatic opponents against Catholic-held territories. Asen managed to avert this threat through diplomatic outreach to Hungary and Constantinople and by refraining from further attacks.[10][11]
Asen broke his alliance with the Latin Empire by the end of 1237 and made a treaty with Vatatzes. According to contemporary historian,George Akropolites, this reversal was prompted by the sudden death of his wife and one of his children from aplague outbreak, which was interpreted asdivine punishment for breaking his previous alliance.[4]
In the years that followed, Asen focused on consolidating Bulgaria's defenses and improving relations with Hungary. The kingdom faced threats not only from a potential crusade but also from the northeast, where the Mongols andTatars had destroyed the Cuman state. This new danger imperiled both Bulgaria and Hungary and effectively halted any potential expansions to the south.[12]
After the dissolution of the besieging army, some of John of Brienne's soldiers left his service because they were not paid, further weakening the defenses of the city.[13] In 1237, the emperor recruited Western knights for the defense of the city in his trip west with the help of the pope.[10] Two years later, more knights (estimated 30,000 to 60,000 in number) were mobilized. They crossed Hungary and Bulgaria, where Asen not wanting to fight them gave them free passage. They captured the Nicaean fortress of Tzurulum before dispersing, many returning home and others joining in the defense of Constantinople.[14] The sporadic reinforcements were insufficient to counter the pressure from Nicaean and Bulgarian campaigns, the capital of the Latin Empire was spared only because of the divisions among its enemies.[7]
Vatatzes expanded his holdings in Thrace during the campaign and a year after Asen's death in 1241, he was able to secure Thessaloniki, isolating Constantinople.[15] At the same time, Vatatzes had to return to defend his homeland in Anatolia against a possible Mongol invasion. Nicaea was spared, because the Mongols retreated following the sudden death ofGreat Khan inKarakorum. It was a boon for Nicaea because Mongols had inflicted great damage to theSeljuk Empire, leaving Nicaea in a stronger position to claim Constantinople.[16]
In 1258, theBattle of Pelagonia signaled the beginning of the end of Latin predominance in Greece. On 25 July 1261, with most of the Latin troops away on campaign, the Nicaean generalAlexios Strategopoulos found an unguarded entrance to the city, and entered it with his troops, restoring the Byzantine Empire underMichael VIII Palaiologos.[17]
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