In the first millennium B.C, different parts of the Ukraine were under different rules, such as Cimmerians, Sarmatians and Scythians. When the time turned to the 1st millennium A.D, it was ruled by Goths, Huns, Bulgars, Avars, Khazars and Magyars. After the 4th century Slavic tribes were settled there. In that time Kiev was its major town. The Kievan power was ended in the middle of 13th century after the Mongol conquest. The territory was ruled by Lithuania in the 16th century and in the 17th century it was ruled by Poland. Ukraine was under the Russian rule in the time of 18th century. The Ukrainian National Republic was established in the year of 1917. In the time of 1918, it declared their freedom from Russia. But again in the very next year it was re-conquered. Ukraine became a part of U.S.S.R as Ukrainian Soviet Socialist Republic in the year of 1923. Poland held the northwestern region of the country from 1919 to 1939. More than five million Ukrainians died of hunger in an unparalleled peacetime tragedy under the Soviet leader Joseph Stalin in 1932-33. The country was suffered by Axis army during the Second World War, in the year of 1941. Ukraine was re-occupied by the Soviet Russia in the year of 1944. It was the site of the Soviet built nuclear power plants and in the year of 1986 the Chernobyl accident was taken place in that territory. Ukraine became an independent country in the year of 1991.