Islam entered southern Europe through the invading "Moors" of North Africa in the 8th–10th centuries. Many kingdoms and duchies in Spain, Portugal, Southern Italy and Malta have existed for centuries. After a series of conflicts and wars known as the Reconquista, these areas became Christian. Islam expanded into the Caucasus through the Muslim conquest of Persia in the 7th century. The Ottoman Empire expanded into southeastern Europe; it conquered large parts of the Byzantine Empire in the 14th and 15th centuries. Later, the power of the Ottoman empire faded, and it lost most of its territories in Europe. It collapsed in 1922. The countries of the Balkans still have large populations of native Muslims. Many of these Muslims have become secular. 