In 1344, Momchil, the independent Bulgarian ruler of the Rhodope and Aegean regions, whose army grew to 2,000 men, took an important role in the Byzantine civil war. While at first he supported John Kantakouzenos, from the spring of 1344 Momchil reneged, provoked by the aggression of the Ottoman allies. In June he defeated the Ottoman fleet near the Portogalos bay. According to sources, at night the Bulgarian ruler sent boats to burn the anchored Ottoman ships and soon after he defeated the army of Kantakouzenos at Mosynopolis.