Byzantine conquest of Bulgaria

From c. 970 until 1018, a series of conflicts between the Bulgarian Empire and the Byzantine Empire led to the gradual reconquest of Bulgaria by the Byzantines, who thus re-established their control over the entire Balkan Peninsula for the first time since the 7th-century Slavic invasions. The struggle began with the incorporation of eastern Bulgaria after the Russo-Byzantine War (970–971). Bulgarian resistance was led by the Cometopuli brothers, who – based in the unconquered western regions of the Bulgarian Empire – led it until its fall under Byzantine rule in 1018.

As the Byzantine-Bulgarian relations deteriorated by the end of the 960s, the Eastern Roman Empire paid the Kievan prince Sviatoslav to attack Bulgaria. The unexpected collapse of Bulgaria and Sviatoslav's ambitions to seize Constantinople caught the Eastern Roman Empire off-guard but they managed to pull back the Kievan armies and occupied eastern Bulgaria including the capital Preslav in 971. Emperor Boris II was captured and taken to Constantinople where he abdicated and the Byzantine Emperor John I Tzimiskes announced the annexation of Bulgaria, even though the Eastern Roman Empire only controlled Eastern Bulgaria at the time, and the lands to the west remained under Bulgarian control. The four brothers David, Moses, Aron, and Samuel of the Cometopuli dynasty ruled in the free territories and in 976, launched a major offensive against the Byzantines to regain the lost lands. Soon, the youngest brother, Samuel, took complete authority following the deaths of his three eldest brothers.

Samuel proved to be a successful general inflicting a major defeat on the Byzantine army, commanded by Basil II at the Gates of Trajan and retaking north-eastern Bulgaria. His successful campaigns expanded the Bulgarian borders into Thessaly and Epirus and in 998, he conquered the principality of Duklja.