The Latin States in Greece
The agreements with the Venetians laid down in the so-called partitio Romaniae (or the “division of the Roman Empire”) led to the division of the Byzantine Empire into a number of Latin states. Where Boudewijn was allowed a quarter of the territory, three quarters was divided among the many knights.
Boniface of Montferrat took possession of Thessaloniki with the support of the Venetians (to whom he attributed Crete). Nominally he fell under the Emperor of Constantinople, but as king he could actually do whatever he wanted. Boniface immediately turned to the south, where he achieved the necessary success despite fierce resistance from Byzantine governor Leon Sgouros (who had conquered his own state). In 1204 Boniface conquered Athens, which he gave as a fief with Thebes to Duke Otto de la Roche. However, his kingdom was short-lived: as early as 1224, the kingdom of Thessalonica fell prey to Theodoros I Archangelos, the Byzantine ruler of the despotate of Epirus. The Empire of Nicaea also strived to conquer Northern Greece, and after the Bulgars first chased the despotate of Epiros from Macedonia and Thessaly, the “emperor of Nicaea” John Vatatzes in turn succeeded in expelling the Bulgars weakened by death of their ruler Tsar Iwan Asen II and the attacks of the Mongols. In 1246 Vatatzes also conquered Thessaloniki, after which the despotate of Epiros surrendered and Vatatzes recognized as emperor.
William de Champlitte and Godfrey de Villehardouin conquered the Peloponnese between 1204 and 1205, where they initially operated as feudal lords to the king of Thessaloniki. As The Principality of Achaia, this conquest would last for a long time. Especially in the beginning, the collaboration with Otto de la Roche, the Duke of Athens, was very cordial.
Finally, the Venetians, who had received Crete from Boniface of Montferrat in 1204 and later bought some islands in the Aegean Sea from him, seized Kephallonia in 1209, Euboia in 1211 and Kerkyra (Corfu) in 1215. Together with the extreme southern tip of the Peloponnese (at Korone), these islands were the most important points of support for the Venetians for their fleet in trade with Constantinople.