Nearly 172,000 Koryo-saram were forcibly transferred from the Russian Far East to unpopulated areas of the Kazakh SSR and the Uzbek SSR in 1937 by the NKVD on the orders of Soviet leader Joseph Stalin and Chairman of the Council of People's Commissars of the Soviet Union Vyacheslav Molotov. One hundred twenty-four trains were used to resettle them 6,400 kilometres (4,000 mi) to Central Asia. The reason was to stem "the infiltration of Japanese espionage into the Far Eastern Krai", as Koreans were at the time subjects of the Empire of Japan, which was the Soviet Union's rival. It has been described as part of Stalin's policy of "frontier cleansing". Estimates based on population statistics suggest that between 16,500 and 50,000 deported Koreans died from starvation, exposure, and difficulties adapting to their new environment in exile.