Jews were prevented from leaving German-occupied Poland by the "Schutzstaffel" (SS). About 10% of the Polish Jewish population, including nearly 1 million Poles, were rounded up by the Russians and sent to Siberia in intolerable circumstances. They were enslaved, and died from harsh treatment at the hands of the Russians from 1939 and 1943 and onwards. Other Jews were spared harsh treatment, however, and some were trained in Moscow, so as to be fit to command a new Polish government after the war was over. Some of them were sent to remote areas of the Soviet Union, Siberia, or Central Asia.