Today's Bulgarians speak a language that has had Russian smothering since the 19th century, hence, it is not the same as it were, say, a few centuries ago.

http://www.macedoniantruth.org/forum/showthread.php?t=1280

Bulgarians are an unfortunate Slavic-speaking group in Thrace that has adopted the name of their former Mongolic conquerors as an ethnic identity.