The three periods, 1937-8, 1939-43, and 1944-5 were the principal phases of the Communist movement during the Sino-Japanese War. The outbreak of war transformed the political and military environment for all Chinese parties and forced the Chinese Communists into fundamental reconsideration of all important policies, of strategy and of tactics. The principal issues confronting Party Central during the first year and a half of the war were the following: The united front; Military strategy and tactics; and Leaders and leadership. At the outbreak of the war, Mao Tse-tung's position in the Chinese Communist movement was that of primus inter pares. The Communists used the euphemism ' friction' to describe their conflicts with the Nationalists during the middle years of the war. Chinese Communist Party and its principal armies expanded greatly during the Sino-Japanese War. The Japanese were preparing for their greatest military offensive in China since 1937-8, Operation Ichigo.