The Bulgarians are very similar to the Sicilians, only the Sicilians can play a little more defensively and then try to retake the map with UT. The Bulgarians, on the other hand, must always play very aggressively.
As far as I am concerned, the starting mistake was to make the Bulgarians also an infantry civilisation. When in fact historically they were known to get chased by the enemy army and then charge in turn with devastating force. But I digress.