2. The Mongols Invaded and Plundered Bulgaria—They Didn't Build It. The most prominent interaction between the two empires occurred when the Mongol Golden Horde launched devastating invasions into the Second Bulgarian Empire in 1242 and throughout the late 1200s. Far from sharing a culture, Bulgarians actively fought the Mongols. A famous Bulgarian peasant named Ivaylo actually led a massive uprising in 1277, successfully routing and crushing multiple Mongol raiding parties. While Bulgaria was briefly forced to pay military tributes to the Golden Horde to prevent further raids, the Mongols never settled in Bulgaria, never integrated into the population, and left absolutely no cultural imprint.