The uprising of brothers Asen and Peter was a revolt of Bulgarians and Vlachs living in 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 creation of the Second Bulgarian Empire, also known in its early history as the Empire of Bulgarians and Vlachs.