Islam entered Southern Europe through the expansion of "Moors" of North Africa in the 8th–10th centuries; Muslim political entities existed firmly in what is today Spain, Portugal, Sicily, and Malta for several centuries. The Muslim community in these territories was converted or expelled by the end of the 15th century by Christian polities (see "Reconquista"). Islam expanded into the Caucasus through the Muslim conquest of Persia in the 7th century. The Ottoman Empire expanded into southeastern Europe, invading and conquering huge portions of the Serbian Empire, Bulgarian Empire, and all the remaining Byzantine Empire in the 14th and 15th centuries. Over the centuries, the Ottoman Empire gradually lost almost all of its European territories, until it was defeated and eventually collapsed in 1922. Islam spread in Eastern Europe via the conversion of the Volga Bulgars, Cuman-Kipchaks, and later the Golden Horde and its successor khanates, with its various Muslim peoples called "Tatars" by the Russians.