This groundbreaking study on the forging of Chinese communism in the furnace of the anti-Japanese war focuses on North China, where the Chinese Communist Party first took root and later expanded to conquer China. Whilst the explosive growth of the Chinese communist movement during the war years is a fact, the nature of this expansion remains disputed. Here the author examines a set of interrelated issues that have so far not received comprehensive treatment with regard to the main communist base areas in North China – regions where the CCP secured most of its recruits and where its policy programmes were most severely tested by Japanese military campaigns. The analysis centres on how the CCP strove to combine two objectives that it perceived as crucial to building up a sustained mass resistance movement to the Japanese: socio-economic and political restructuring in favour of the poor and the forging of a grassroots rural united front including all social strata. The author also stresses the host of severe constraints that the party’s policy ambitions ran up against, such as massive destruction of the local economy by the Japanese army, the economic burden of running the resistance, peasant ambivalence to revolutionary changes, and the shortage of trained cadres. Ultimately, the movement spread too rapidly and too widely for the party centre to exert more than a very weak or mediated vanguard function outside scattered enclaves. This in turn allowed localities an autonomous dynamic that often conflicted with higher party echelons. Nevertheless, the movement had a broad, if highly uneven, redistributive impact on power resources in the region, leading to a structural fluidity that lowered the barriers to a future revolution. History accelerated.