The whole region of Moesia except for Varna was quickly liberated and the brothers started attacking the Byzantine garrisons to the south of the Balkan Mountains.

In order to change that situation, the Byzantine Emperor, Isaac II Angelos, decided to move the military actions to northern Bulgaria and strike directly to the rebel's heartlands around Tarnovo.

In the spring of the following year, the campaign was resumed, but the element of surprise was gone and the Bulgarians had taken measures to bar the way to their capital Tarnovo.

Their only success was the capture of Asen's wife in an ambush, but Isaac was forced to accept a truce thus de facto recognizing the restoration of the Bulgarian Empire.

The peace lasted until 1189 when, due to the Bulgarian proposal to support the Third Crusade against the Byzantines, Isaac Angelos launched another campaign and suffered a heavy defeat in the Battle of Tryavna.