In the late autumn of 1186, the Byzantine army marched northwards through Sredets (Sofia). The campaign was planned to surprise the Bulgarians. However, the harsh weather conditions and the early winter postponed the Byzantines and their army had to stay in Sredets during the whole winter.

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. Instead the Byzantines besieged the strong fortress of Lovech. The siege lasted for three months and was a complete failure. Their only success was the capture of Asen's wife, but Isaac was forced to accept a truce thus de facto recognizing the restoration of the Bulgarian Empire.