Battle of Kleidion and the conquest of Bulgaria

Basil II had been at war with Samuel since 976 and was defeated by him at the Gates of Trajan in 986; from 1000 onwards, as the historian John Skylitzes put it, he invaded Bulgaria every year, destroying and devastating everything in his way. In the summer of 1014 Samuel blocked the Strumitsa valley near the village of Kleidion ("the key", today's Klyuch) with ditches and a strong wooden wall. Byzantine assaults on the wall failed, and a Bulgarian diversion towards Thessalonica was defeated by the governor Theophylact Botaneiates, but Xiphias found a path over Belasitsa and on 29 July fell on the defenders from behind while Basil stormed the wall. Thousands of Bulgarians were killed or captured; Samuel escaped thanks to his son Gabriel Radomir.

According to Skylitzes, after Botaneiates had been ambushed and killed in the passes, Basil had the prisoners — 15,000 of them, or 14,000 according to Kekaumenos — blinded, leaving one eye to one man in every hundred so that he could lead the others home; at the sight of them Samuel suffered a heart attack and died on 6 October 1014. Some modern historians, such as Vasil Zlatarski, consider these numbers exaggerated, and Paul Stephenson argues that Basil was not called "Bulgar-slayer" (Boulgaroktonos) until the late 12th century, when wars with the Bulgarians began again. Resistance continued under Samuel's successors Gabriel Radomir and Ivan Vladislav until Ivan Vladislav was killed before Dyrrhachium in 1018. The Bulgarian nobles then submitted; Basil gave many of them titles and commands, let the new province pay its taxes in kind and celebrated his triumph in Athens. Bulgaria remained part of the empire until the rising of the Asen brothers in 1185, and Byzantium again held the Danube frontier.