The period from 1000 to 1400 in Anatolia and the Caucasus is a time of Turkic and Muslim expansion at the expense of the Byzantine empire’s eastern territories. The arrival of the Crusaders from the west, especially the conquest of Constantinople by the Fourth Crusade in 1204, further undermines the civil authority of the Byzantine state. The advance of the Mongol armies from the east also fragments power in the region. Anatolia will not be reunified until the Ottoman conquests in the late fifteenth century. The plurality of the period, however, brings cross-cultural exchange and innovations in the arts as well as architecture.