It initially consisted only of the teritories between the Balkan Mountains and Danube, but they will soon also include current Romania, a section of Serbia and western Macedonia.
John Asen II, the fifth ruler of the Asen dynasty, will add western Thrace and part of Albania by 1230.
The kingdom started to disintegrate after the death of John Asen II, and its armies were defeated in 1330, then the armies of the Ottoman Empire controlled all Bulgaria by 1396