Uprising of Asen and Peter The Uprising of 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 at the turn of the year 1185 / 1186 and ended with the creation of the Second Bulgarian Empire , ruled by the Asen dynasty . Isaac II Angelus , in order to raise money for the wedding of the daughter of King Bela 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 . After their return , many of the protesters were unwilling to join the rebellion . The brothers Peter and Asen built the Church of St Demetrius of Thessaloniki in Tarnovo , dedicated to Saint Demetrius , who was traditionally considered a patron of the Byzantine city of Thessaloniki , and claimed that the Saint had ceased to favour the Byzantines : " God had decided to free the Bulgarians and the Vlach people and to lift the yoke that they had borne for so long " . This persuaded their followers to attack Byzantine cities , seizing prisoners and cattle . Preslav , capital of the First Bulgarian Empire , was raided , and it was after this symbolic incident that Peter assumed the insignia of Tsar ( or Emperor ) . In the spring of 1186 , Isaac started a counter - offensive . It was successful at first . During the solar eclipse of 21 April 1186 , the Byzantines successfully attacked the rebels , many of whom fled north of the Danube , making contact with the Cumans . In a symbolic gesture , Isaac II entered Peter ' s house and took the icon of Saint Demetrius , thus regaining the saint ' s favour . Still under threat of ambush from the hills , Isaac returned hastily to Constantinople to celebrate his victory . Thus , when the armies of Bulgarians and the Vlachs returned , reinforced with their Cuman allies , they found the region undefended and regained not only their old territory but the whole of Moesia , a considerable step towards the establishment of a new Bulgarian state . The Emperor now entrusted the war to his uncle , John the sebastocrator , who gained several victories against the rebels but then himself rebelled . He was replaced with the emperor ' s brother - in - law , John Cantacuzenus , a good strategist but unfamiliar with the guerrilla tactics used by the mountaineers . His army was ambushed , suffering heavy losses , after unwisely pursuing the enemy into the mountains . The third general in charge of fighting the rebels was Alexius Branas , who , in turn , rebelled and turned on Constantinople . Isaac defeated him with the help of a second brother - in - law , Conrad of Montferrat , but this civil strife had diverted attention from the rebels and Isaac was able to send out a new army only in September 1187 . The Byzantines obtained a few minor victories before winter , but the rebels , helped by the Cumans and employing their mountain tactics , still held the advantage . In the spring of 1188 , Isaac attacked the fortress of Lovech , but failed to capture it after a three - month siege . The lands between the Haemus and the Danube were now lost to the Byzantine Empire . The Emperor ' s only consolation was to hold , as hostages , Asen ' s wife and a certain John ( future Kaloyan of Bulgaria ) , brother of the two new leaders of the Bulgarian state .