13. – Bulgaria at the time of Assen II.

The Bulgarian people gained its full political and national unity under the reign of Iwan Assen II (1216-1240), son of Assen I. Thanks to his foresight and political fitness, this czar prepared in a very apt manner the downfall of his rival Theodore Angelos Komnenos, the Despot of Epirus, who, at the time of the weak czar Boril, had subjected the Bulgarian territories in the south-west, and who even brought about the conquest of Salonica. Theodore proclaimed himself Emperor of Salonica in 1223, and made preparations to rescue Constantinople from the rulership of the Latins in order to ascend the Byzantine throne himself. But as Theodore Komnenos first had to get rid of his rival, the Bulgarian czar, he, above all, resolved to make an end of Iwan Assen, so he maliciously declared war against him. Thls war ended in 1230 with the celebrated battle of Klokotnitza (the present village Semidje, north-east of Haskowo) where Theodore and his followers were taken prisoners by the Bulgarian czar.

After this event all his territories, including Albania, were incorporated in the Bulgarian State. Thessaly and Salonica, and their districts, formed a "Despotia" under the protectorate of fhe Bulgarian czar; the administration was entrusted to Manuel, Theodore Komnenos's brother, who was the son-in-law of Iwan Assen.

This map shows the enlargement of the Bulgarian State after the victory of Klokotnitza.