males were forced to enlist in the Bulgarian army. Although Basil II sent forces to the region, they were defeated. With this victory, Bulgaria had gained influence over most of the southwestern Balkans, although it did not occupy some of these territories. From Larissa, Samuel took the relics of Saint Achilleios, which were laid in a specially built church of the same name on an island in Lake Prespa. The Bulgarian successes in the west raised fears in Constantinople, and after serious preparations, Basil II launched a campaign into the very centre of the Bulgarian Empire to distract Samuel from southern Greece. The Byzantine army passed through the mountains around Ihtiman and besieged Sredets in 986. The Byzantines assaulted the city for 20 days, but their attacks proved fruitless and costly: the Bulgarians came out of the city several times, killed many enemy soldiers and captured draught animals and horses. Eventually, the Bulgarian troops burned the siege equipment of the Byzantine army, forcing Basil II to withdraw to Thrace, but on 17 August 986, while passing through the mountains, the Byzantine army was ambushed and routed at the Trajan's Gates Pass. This was a significant blow for Basil, who was one of the few to return to Constantinople; his personal treasure was captured by the victors. After the defeat, the rebellion of Bardas Phocas diverted the efforts of the Byzantine Empire into another civil war.<ref>Ostrogorsky, G. History of the Byzantine state (Istorija Vizantije', Исторijа Византиje), pp. 397–398.</ref> Samuel seized the opportunity and began to exert pressure on Thessaloniki.Rozen, p. 27. Basil II sent a large army to the town and appointed a new governor, Gregorios Taronites, but he was powerless to stop the Bulgarian advance. By 989, the Bulgarian troops had penetrated deep into Byzantine territory, and seized many fortresses, including such important cities as Veria and Servia. In the south, the Bulgarians marched throughout Epirus and in the west they seized the area of modern Durrës (medieval Dyrrhachium or Drach) on the Adriatic Sea. In 989, Phocas was killed and his followers surrendered, and the following year Basil II reached an agreement with Skleros. The Byzantines focused their attention on Bulgaria, and counter-attacked in 991.Stephen of Taron, p. 198. The Bulgarian army was defeated and Roman was captured while Samuel managed to escape. The Byzantines conquered some areas; in 995, however, the Arabs invaded Asia Minor and Basil II