 In the spring of 1279, Ivaylo managed to break through the Mongol blockade at Drastar and besieged Tarnovo. This advance took Ivan Asen III and his supporters by surprise. Michael VIII took measures to protect his protégé and in the summer of 1279 sent a 10,000-strong army under the command of the protovestiarios Murin. Ivaylo did not linger in Tarnovo and engaged the invading host on 17 June 1279 in the Kotel Pass. Despite being outnumbered, in the ensuing battle near the fortress of Devina the Bulgarians achieved a complete victory. Part of the Byzantines perished in the battle along with their commander, the rest were captured and killed by orders of Ivaylo. A month later, the Byzantines sent another army of 5,000 troops led by the protovestiarios Aprin. Ivaylo engaged them in the eastern Balkan Mountains on 15 August 1279 and after a long combat defeated the Byzantines, personally killing Aprin in the process. Ivaylo was said to had "fought with fury, achieving many feats" in both battles.
