Theodore Peter of Bulgaria in the context of "Bulgarians"

The Byzantine–Bulgarian wars were a series of conflicts fought between the Byzantine Empire and the Bulgarian Empire which began after the Bulgars conquered parts of the Balkan peninsula after 680 AD. The Byzantine and First Bulgarian Empire continued to clash over the next century with varying success, until the Bulgarians, led by Krum, inflicted a series of crushing defeats on the Byzantines. After Krum died in 814, his son Omurtag negotiated a thirty-year peace treaty. Simeon I had multiple successful campaigns against the Byzantines during his rule from 893 to 927. His son Peter I negotiated another long-lasting peace treaty. His rule was followed by a period of decline of the Bulgarian state.

In 971 John I Tzimiskes, the Byzantine emperor, subjugated much of the weakening Bulgarian Empire by defeating Boris II and capturing Preslav, the Bulgarian capital. Samuel managed to stabilize the Bulgarian state with its center around the town of Prespa. Near the end of his rule, the Byzantines regained the upper hand, and under Basil II they won the Battle of Kleidion and completely conquered Bulgaria in 1018. 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 quash the revolt.

The Uprising of Asen and Peter (Bulgarian: Въстание на Асен и Петър) was a revolt of Bulgarians and Vlachs living in Moesia and the Balkan Mountains, then the theme of Paristrion of the Byzantine Empire, caused by a tax increase. It began on 26 October 1185, the feast day of St. Demetrius of Thessaloniki, and ended with the restoration of Bulgaria with the creation of the Second Bulgarian Empire, ruled by the Asen dynasty.

Isaac II Angelus, in order to raise money for his wedding with the daughter of King Béla III of Hungary, levied a new tax which fell heavily on the population of the Haemus Mountains. They sent two leaders (Peter and Asen) to negotiate with the emperor at Kypsella (now İpsala) in Thrace. They asked to be added to the roll of the Byzantine army and to be granted land near Haemus to provide the monetary income needed to pay the tax. This was refused, and Peter and Asen were treated roughly. Their response was to threaten revolt.