Struggle for Constantinople

Struggle for Constantinople
Part of the Byzantine–Latin wars, Byzantine–Bulgarian wars, Byzantine–Seljuk wars, Bulgarian–Latin wars, and the Crusades
The Entry of the Crusaders in Constantinople, by Eugène Delacroix
Date 12 April 1204 – 25 July 1261 (57 years, 3 months and 13 days) Location The Balkans and Anatolia Result Nicene victory Territorial changes The Empire of Nicaea captures Constantinople and restores the Byzantine Empire.
Belligerents
Latin states: Latin Empire Kingdom of Thessalonica (1204–1224) Principality of Achaea Duchy of Philippopolis (1204–1208) Duchy of Athens Duchy of the Archipelago Republic of Venice	Byzantine states: Empire of Nicaea (1205–1261) Empire of Thessalonica (1225–1242) Empire of Trebizond Despotate of Epirus Despotate of Thessaly (1239–1261)	Others: Second Bulgarian Empire Sultanate of Rum Kingdom of Serbia Kingdom of Sicily Mongol Empire (1241–1243)

The struggle for Constantinople^[1][2][3] was a complex series of conflicts following the dissolution of the Byzantine Empire by the Fourth Crusade in 1204, fought between the Latin Empire established by the Crusaders, various Byzantine successor states, and foreign powers such as the Second Bulgarian Empire and Sultanate of Rum, for control of Constantinople and supremacy in the former empire's territory.

The Byzantine Empire was at the time of the Fourth Crusade already divided by internal revolts. In the aftermath of the Crusader sack of Constantinople, the empire was dissolved into a patchwork of pretenders and warlords. The former Byzantine emperors Alexios III and Alexios V both aspired to retake the capital, though were defeated by the Latins. The early years after 1204 saw the rise and fall of numerous Byzantine statelets; the Latins managed to defeat warlords such as Leo Sgouros but were unable to halt the formation of the more well-organized Empire of Nicaea, Empire of Trebizond, and Despotate of Epirus. The prospect of a swift Latin conquest of the entire former empire ended when the Bulgarian ruler Kaloyan defeated the Latin army at the Battle of Adrianople (1205).

In 1205–1209, the Empire of Nicaea transitioned into a proper empire-in-exile, with Theodore Laskaris crowned as emperor by a self-appointed Ecumenical Patriarch of Constantinople-in-exile. The Nicene emperor and his patriarch were not accepted as legitimate by the other Byzantine pretenders. An attempted two-front attack on both Epirus and Nicaea by the Latin emperor Robert of Courtenay in 1223/1224 ended in disaster and the Latin Empire thereafter only survived through the rivalry between its enemies. In 1224, Theodore Komnenos Doukas of Epirus captured Thessalonica, the second most important city of the former empire. Komnenous Doukas likewise had himself crowned emperor, establishing the Empire of Thessalonica, and came close to recapturing Constantinople before being defeated by Bulgaria at the Battle of Klokotnitsa in 1230.

After Klokotnitsa, Ivan Asen II of Bulgaria aspired to himself restore the Byzantine Empire, variously allying with and opposing the Nicene emperor John Doukas Vatatzes. In the early 1240s, Bulgaria was weakened by Ivan Asen's death and pressure from the Mongol Empire. During the Mongol invasion of Anatolia, Sultan Kaykhusraw II of Rum was—despite support by Christian forces sent by the Latin, Nicene, and Trapezuntine empires—defeated at the Battle of Köse Dağ (1243) and forced to become a Mongol vassal. The weakening of Bulgaria and Rum allowed John Doukas Vatatzes to rapidly expand into the Balkans. Although opposed by Bulgaria, the Thessalonian successor states, and the remaining Latin lords of Greece, the Nicenes under Michael Palaiologos ultimately captured Constantinople in 1261, restoring the Byzantine Empire.

Conflicts resulting from the struggle for Constantinople plagued much of the later reign of Michael Palaiologos (1261–1282). Despite challenges, Palaiologos managed to ensure the safety of the restored empire, which survived for two centuries under his descendants, until its fall in 1453.