In 1931 the Japanese launched its invasion and subsequent occupation of Manchuria. Chiang Kai-shek, who led the central government of China, decided that China must avoid all-out war with Japan due to domestic turmoil and inadequate preparation. Therefore, he "pursued a strategy of appeasing Japan while struggling for real national unity and over time sufficient strength to confront the Imperial army. This appeasement policy lasted for another six years". Even though his campaigns against the Communists resulted in their retreat and a 90% reduction in their fighting strength, he was unable to eliminate their forces entirely, and his policy of "internal pacification before external resistance" (:) was very unpopular with the Chinese populace, which caused widespread resentment against the ruling KMT leadership and its regional warlord allies.