The defeat of Samuel at Ohrid began a period of Byzantine political and cultural domination over the region. Especially influenced were the Orthodox religion and art styles, the effects of which can still be seen today in the innumerable icons throughout Bulgaria's churches and markets. The Bulgarians staged several rebellions, but also had to deal with renewed attacks from northern groups coming down across the Danube, most notably the Magyars.
The Byzantines were successful in keeping down these uprisings until the late 12th century, when bolyari (noble) brothers Petar and Assen led a victorious battle against the empire's army. They founded the Second Bulgarian Kingdom, with a new capital in the city of Veliko Turnovo. The brothers successfully fought off successive Byzantine attempts to take back the area in 1187 and 1190, and then set about expanding into the previous territory of the First Bulgarian Empire. First capturing Varna on the Black Sea coast and then pressing south into Thrace and east into Macedonia, the Second Kingdom steadily grew, particularly taking advantage when Constantinople was sacked by the Crusaders in 1204. Under Tsar Ivan Assen II (1218-41) the medieval Kingdom was again expanded to reach the Adriatic and the Aegean, and it was once more a time of prosperity and growth.
Veliko Turnovo, the capital of Second Bulgarian Kingdom
However, after Assen's death, instability set in as the Mongols retreated from their invasions in central Europe by trekking through Serbia and Bulgaria, laying waste to the lands they traversed. This left a weakened state prime for the Byzantines to once more attack, and they promptly took back much of Thrace. A group of Mongols called the Tartars settled on the far shores of the Black Sea and continued to randomly sweep down and attack from the north. Various other skirmishes with their Byzantine rivals as well as with the rising Serbian power to the west served to further weaken the Bulgarian state. Internal conflict and dissonance among the nobles, or bolyari, sealed Bulgaria's fate as it lost its unity, and mistrust between the Balkan powers created an atmosphere which was not at all conducive to forging alliances against the new regional threat from the east.
