THE UNEXPECTED ESTABLISHMENT of the Latin empire of Constantinople in 1204 altered the balance of power in South-Eastern Europe significantly. The conquered territories were divided among the participants in the crusade; the Byzantine aristocracy was able to wrestle away some peripheral areas such as Nicaea, Epirus, and Trebizond, and slowly build successful polities that, in time, posed a grave threat to the Latin rule, eventually causing its demise. The imperial borders were also menaced by the kingdom of Bulgaria, ruled at that time by Kalojan. He was the third tsar of the newly restored Bulgarian state, which had regained its independence from Byzantium in 1185/ 86 after a successful revolt led by Kalojan's elder brothers, Asen and Petăr. Leading a coalition of Bulgarians and Vlachs, with the invaluable help of the Cumans, they seceded from the Byzantine Empire and conquered a large territory stretching from the Danube to the Stara Planina massif; their capital city was the previously unimportant town of Tărnovo.

Kalojan was crowned in 1197 after the death of his brother Petăr, killed by an unknown assassin. During the first years of his reign, Kalojan apparently did not engage in major confrontations with the Byzantine Empire on Bulgaria's southern frontier like his brothers had done continuously in the past years. Instead, he occupied the region of Braničevo to the northwest, thus reaching the borders of Hungary; he also continued to enlist the help of his Cuman allies, who systematically raided Thrace and Macedonia. It is possible that Bulgarian and Vlach troops participated in the operations, whose aim was not, however, the conquest of new lands, but rather to amass plunder. Kalojan also supported two separatists of Bulgarian origin, Ivanko (who had murdered Kalojan's brother Asen in 1195, sought refuge in Constantinople, and then betrayed the empire as well) and Dobromir Chrysos, an otherwise unknown character. The former created an autonomous dominion in the Rhodopes, while Chrysos was based in the Macedonian fortress of Prosakon. Neither uprising lasted long, but while they existed they created substantial problems for the Byzantine Empire. Ivanko was captured in 1200 and his lands returned to imperial control.