and joined the Hungarian forces. At the same time, a strong Byzantine army besieged Vidin, Ahtum's seat. Although many soldiers were required to participate in the defense of the town, Ahtum was occupied with the war to the north. After several months he died in battle when his troops were defeated by the Hungarians. As a result of the war, Bulgarian influence to the northwest of the Danube diminished. Further Byzantine successes The Byzantines took advantage of the Bulgarian troubles in the north. In 1003, Basil II led a large army to Vidin, northwestern Bulgaria's most important town. After an eight-month siege, the Byzantines ultimately captured the fortress, allegedly due to betrayal by the local bishop. The commanders of the town had repulsed all previous attempts to break their defence, including the use of Greek fire. While Basil's forces were engaged there, Samuel struck in the opposite direction: on 15 August he attacked Adrianople and plundered the area. Basil II decided to return to Constantinople afterwards, but, fearing an encounter with the Bulgarian army on the main road to his capital, he used an alternate route. The Byzantines marched south through the Morava valley and reached a key Bulgarian city, Skopje, in 1004. The Bulgarian army was camping on the opposite side of the Vardar River. After finding a ford and crossing the river, Basil II attacked and defeated Samuel's unsuspecting army, using the same tactics employed at Spercheios. The Byzantines continued east and besieged the fortress of Pernik. Its governor, Krakra, was not seduced by Basil's promises of a noble title and wealth, and successfully defended the fortress. The Byzantines withdrew to Thrace after suffering heavy losses.Zlatarski, pp. 685–687. In the same year, Samuel undertook a march against Thessaloniki. His men ambushed and captured its governor, Ioannes Chaldus,Actes d'Iviron I. Des origines au milieu du XIe siècle, Archives de l'Athos XIV, eds. J.Lefort, N.Oikonomides, D.Papachryssanthou, H.Métrévéli (Paris, 1985), doc. 8 but this success could not compensate for the losses the Bulgarians had suffered in the past four years. The setbacks in the war demoralized some of Samuel's military commanders, especially the captured Byzantine nobles. Samuel's son-in-law Ashot, the governor of Dyrrhachium, made contact with the local Byzantines and the influential John Chryselios, Samuel's father-in-law. Ashot and his wife boarded one of the Byzantine ships that were beleaguering the town and fled to Constantinople. Meanwhile, Chryselios surrendered the city to