North and South Korea both suffered from the massive destruction caused during the Korean War. Historian Charles K. Armstrong stated that "North Korea had been virtually destroyed as an industrial society". In the years immediately after the war, North Korea mobilized its labour force and natural resources in an effort to achieve rapid economic development. Large amounts of aid from other communist countries, notably the Soviet Union and the People's Republic of China, helped the country achieve a high growth-rate in the immediate postwar period.