Final Battle of Thessaloniki

News of the success of Peter Delyan's uprising, which began in Belgrade in early 1040, quickly reached Armenia, where many Bulgarian nobles had been settled after the fall of the First Bulgarian Empire in 1018. The most influential of them was Alusian, the second son of the last Bulgarian tsar, Ivan Vladislav. Disguised as a mercenary, he left Armenia and travelled to Constantinople. Despite all the difficulties and strict controls, Alusian managed to reach the Bulgarian lands. He took refuge in the camp of the rebels led by Peter II Delyan. There he intended to overthrow Peter II Delyan and become the military leader himself. Although Delyan suspected Alusian of harbouring hostile intentions, he gave him an army to attack Thessaloniki. Alusian accordingly marched towards Thessaloniki with it.

Alusian made poor decisions in commanding the army, and his soldiers were exhausted when they reached Thessaloniki. There, the Byzantines crushed them. This defeat worsened relations between Alusian and Delyan. A year later, Alusian blinded Peter II Delyan.