Japan occupied Hong Kong from 1941 to 1945 during the Second World War. By the end of the war in 1945, Hong Kong had been liberated by joint British and Chinese troops and returned to British rule. Hong Kong greatly increased its population from refugees from Mainland China, particularly during the Korea War and the Great Leap Forward. In the 1950s, Hong Kong transformed from a territory of entrepôt trade to one of industry and manufacturing. The Chinese economic reform prompted manufacturers to relocate to China, leading Hong Kong to develop its commercial and financial industry.