Since the Treaty of Nymphaeum in 1214, the Latin Empire had controlled the northwestern littoral of Asia Minor, from Nicomedia to Adramyttium, as well as the Mysian plain. In 1222, the energetic founder of the Nicaean Empire, Theodore I Laskaris, died, and was succeeded by his son-in-law, John III Doukas Vatatzes. The succession was disputed by Theodore's brothers, the sebastokratores Isaac and Alexios, who rose up in revolt and requested the aid of the Latin emperor, Robert of Courtenay. At the head of a Latin army, they marched against Vatatzes. The two armies met at Poimanenon, near a church dedicated to the Archangel Michael. In the ensuing battle, Vatatzes achieved a decisive victory; among the captives taken were the two Laskaris brothers, who were blinded.