Following Vatatzes' conquests, the region of Pelagonia in western Macedonia became a border zone between the Nicaean and Epirote domains. When Vatatzes died in 1254, the ruler of Epirus, Michael II Komnenos Doukas (), sponsored a rebellion against Nicaea in Albania, and invaded the Nicaean domains, capturing the fortress of Prilep and the local Nicaean governor, and future historian, George Akropolites. Michael II's advance on Thessalonica was interrupted, however, when Manfred of Sicily () landed his own troops in Albania and captured most of it, as well as Corfu. Like the earlier Norman kings of Sicily, Manfred had his own ambitions in the Balkans, including Constantinople itself; and the enforced residence of his half-sister, Constance, the widow of Vatatzes, at the Nicaean court, only aggravated his feelings towards Nicaea. Thus, when Michael II offered to hand over Albania and Corfu as the dowry of his eldest daughter Helena, Manfred accepted. Michael II now formed a wider anti-Nicaean alliance, by giving his second daughter, Anna, to the Latin Prince of Achaea, William of Villehardouin (), who was also overlord of the other Latin states of southern Greece, the Duchy of Athens and the Triarchs of Negroponte. Michael II also secured the backing of the Serbian king, Stephen Urosh I (), while Vatatzes' son and successor, Theodore II Laskaris (), in turn sought the support of Constantine Tikh of Bulgaria () giving him his own daughter Irene in marriage. Before he could campaign against Epirus, however, he died and was succeeded his young son John IV Laskaris (). Very soon, power was seized by the ambitious aristocrat Michael VIII Palaiologos (), first as regent and then as senior co-emperor. Nicaean expedition against Epirus Michael Palaiologos found himself faced with a powerful coalition that, according to the Byzantinist Donald Nicol, "seemed likely to threaten the possession not only of Thessalonica but even of Constantinople itself". Michael Palaiologos did not tarry. Already in the autumn of 1258, his army crossed over into Europe, under his brother John Palaiologos, who held the quasi-imperial rank of , and the (commander-in-chief) Alexios Strategopoulos, and wintered in Macedonia, where it was joined by local levies. At the same time, Michael Palaiologos sent separate embassies to each of the three main allies, hoping to pry them apart by diplomacy. These efforts failed, as the three allies stood to gain much from a successful offensive against Nicaea. In spring 1259,