The Hundred Regiments Offensive
Communist forces under the Eighth Route Army launched a large-scale offensive against Japanese lines of communication in North China, the single biggest operation the Chinese Communist Party mounted against Japan during the war, damaging rail lines and mines across the region. The scale of Japanese losses is disputed between sources by a factor of ten, and the offensive's main lasting consequence was Japanese: it convinced the occupying command that the Communist base areas were a more serious threat than previously assessed, and helped trigger the Three Alls campaign that followed.