Unable to defend his country from the Ottomans, in 1373 the Bulgarian emperor Ivan Shishman agreed to become an Ottoman vassal and to marry his sister Kera Tamara to their sultan Murad I, while the Ottomans were to return some conquered fortresses.[1] Despite the peace, in the beginning of the 1380s the Ottomans resumed their campaigns and besieged the important city of Sofia which controlled major communication routes to Serbia and Macedonia. There are little records about the siege. After the futile attempts to storm the city, the Ottoman commander Lala Shahin Pasha considered to abandon the siege.[1] However, a Bulgarian renegate managed to lure the city governor ban Yanuka out of the fortress to hunt and the Turks captured him.