Michael's achievements on the battlefield were more positive, although still mixed. He tried to take advantage of a civil war in Bulgaria in the late 1270s, but the Byzantine armies suffered several major defeats at the hands of the peasant Emperor Ivaylo. The Emperor managed to temporarily impose his son-in-law Ivan Asen III on the Bulgarian throne, but after the Byzantine defeat at Devina he had to flee. However, Michael VIII later managed to conquer the Bulgarian portion of Thrace, while the internal situation of the Bulgarian Empire remained unstable. In 1275, Michael VIII sent an army against Thessaly and fleet of 73 ships to harass the Latin states in Greece. The army was crushingly defeated at the Battle of Neopatras, but the fleet won a similarly comprehensive victory at the Battle of Demetrias.