Russia and Ukraine relations have seen a tumultuous array of disturbances and escalations and their common past dates back to at least the late 1700s when the territory — now called Ukraine— became part of the Russian empire after periods of rule under the Mongols, the Poles, and Lithuanians. However, Ukraine declared its independence in 1918, one year after the communist revolution in Russia, but the Red Army eventually took most of it in 1921, turning Ukraine into a republic inside the Soviet Union.