In 1783, Crimea was annexed by the Russian Empire as the result of the Russo-Turkish War (1768–1774). Following the Russian Revolution of 1917, Crimea became an autonomous republic within the Russian SFSR in the Soviet Union. During World War II, Crimea was downgraded to the Crimean Oblast and the entirety of one of its indigenous populations, the Crimean Tatars, were deported to Central Asia, an act recognized as a genocide by Ukraine and three other countries. In 1954, the Soviet Union transferred Crimea to the Ukrainian SFSR from the Russian SFSR.