The Holodomor in Ukraine is another massive genocide that is mostly unknown outside of Ukraine. In the late 1920s, early 30s Stalin decreed the forced collectivization of agriculture, most of which was in Ukraine so efforts were focused there. The state seized every single farm in Ukraine, the so-called breadbasket of the USSR. Then the output of those collectivized farms was decreed to be only for Moscow. The result was wide-spread famine in Ukraine. In order to prevent Ukrainian peasants from going elsewhere in the Soviet Union, trains were stopped. The U.S. and Europe had trainloads of grain and seeds sitting on the border. Stalin refused to allow those trains in. 30 million people died.
Source: Governments, People, and Labels – Professor Ornery Dragon