Lack of stability was eminent in the southern Balkans as well : in 1341–1347 the Byzantine Empire was shaken Motion by a bloody civil war between John V Palaiologos and John VI Kantakouzenos .

During the civil war in Byzantium both Palaiologos and Kantakouzenos were trying to find external allies and used Using foreign mercenaries .

John Kantakouzenos on the other hand Giving regularly hired Employment Ottoman Turk mercenaries from Asia Minor who soon became Becoming a fixture on the battlefields in Thrace .

While at first he supported Supporting John Kantakouzenos , from the spring of 1344 Momchil reneged , provoked Causation by the aggression of the Ottoman allies .

According to sources , at night the Bulgarian ruler sent Sending boats to burn Destroying the anchored Ottoman ships and soon after he defeated Conquering the army of Kantakouzenos at Mosynopolis .

He was replaced Change_of_leadership with the emperor 's brother-in-law , John Kantakouzenos , a good strategist but unfamiliar with the guerrilla tactics used Using by the mountaineers .