After the temporary quiet which followed after 1373, in 1380 the Ottomans again started hostilities. With a large army Sultan Murad moved towards the southwestern regions of the Tarnovo Tsardom with the main objective to seize its center Sofia. After a bloody clash in the Zlatitsa valley the Turks moved on to Sofia and besieged it. The city which was commanded by ban Yanuka repulsed all the attacks of the superior Ottoman forces under Lala Şahin. The later could not continue the siege and was forced to pull back to Odrin where he reported his failure to the Sultan. While he was absent the Turks managed to infiltrate Sofia and one Muslim Bulgarian captured ban Yanuke while hunting and sent him to Lala Şahin who was in Plovdiv at that time. From there the Bulgarian commander was sent back to Sofia and when the defenders saw their captured leader they surrendered the city to the Ottomans (1382).