In 971 John I Tzimiskes, the Byzantine emperor, subjugated much of the weakening Bulgarian Empire, facing wars with Croatians, Magyars, Pechenegs and Russians, by defeating Boris II and capturing Preslav, the Bulgarian capital. Constantinople under Basil II completely conquered Bulgaria in 1018 as a result of the 1014 Battle of Kleidion. There were rebellions against Byzantine rule from 1040 to 1041, and in the 1070s and the 1080s, but these failed. In 1185, however, Theodore Peter and Ivan Asen started a revolt, and the weakening Byzantine Empire, facing internal dynastic troubles of its own, was unable to prevent the revolt from being successful.