The Battle of the Spercheios River

After the major Bulgarian victory at the Gates of Trajan on 17 August 986, civil war broke out in Byzantium. The empire soon also became involved in conflict with the Fatimids over Syria. Samuel exploited the Byzantine armies' commitments in the east to liberate north-eastern Bulgaria, conquered by Byzantium in 971, and gain control of numerous fortresses around Thessaloniki. Following victories over the Byzantines in 995–996, the Bulgarians penetrated deep into Greece, reaching the Peloponnese. To address this serious threat, Emperor Basil II appointed Nikephoros Ouranos governor of all the Balkan territories and sent him against the Bulgarians. Ouranos followed their army and attacked after it crossed Thermopylae on its return from the Peloponnese.

This was Samuel's first military failure. He lost because Ouranos surprised his troops by attacking their camp one night. The Bulgarians could offer no resistance, and many were killed. Samuel and his son barely escaped by hiding among the corpses and pretending to be dead. Immediately after the battle, Samuel promised Basil II that he would submit, but negotiations ended when he learned of Tsar Roman's death. Roman had been a Byzantine prisoner for years, and Samuel proclaimed himself tsar in 997.