A variety of social, cultural, ethnic, and linguistic factors contributed to the sparking of unrest in eastern and southern Ukraine, and the subsequent eruption of the Russo-Ukrainian War, in the aftermath of the early 2014 Ukrainian revolution. Following Ukrainian independence from the Soviet Union in 1991, resurfacing historical and cultural divisions and a weak state structure hampered the development of a unified Ukrainian national identity. In eastern and southern Ukraine, Russification and ethnic Russian settlement during centuries of Russian rule caused the Russian language to attain primacy, even amongst ethnic Ukrainians. In Crimea, ethnic Russians have comprised the majority of the population since the deportation of the indigenous Crimean Tatars by Soviet Union leader Joseph Stalin following the Second World War. This contrasts with western and central Ukraine, which were historically ruled by a variety of powers, such as the Polish–Lithuanian Commonwealth and the Austrian Empire. In these areas, the Ukrainian ethnic, national, and linguistic identity remained intact.