After the major success of the Bulgarians in the Battle of the Gates of Trajan in 986, Byzantium descended into a civil war, further exacerbated by the conflict with the Fatimids in Syria. Tsar Samuil took advantage of the situation and conquered virtually the whole of the Balkan Peninsula, excluding the parts of Thrace closest to Constantinople, and southern Greece. He managed to seize many castles in the surroundings of Byzantium's second largest city Thessalonica. Every year he led campaigns against the Byzantines and plundered their territories. In 991 the Byzantines managed to capture the emperor Roman of Bulgaria but this did not stop Samuil who was now de facto the only emperor of Bulgaria. In 996 he ambushed and destroyed the forces of the strategos of Thessalonica and marched to t