This study looks at the first three years of the Chinese Communists' New Fourth Army, between the late spring of 1938 and January 1941. The New Fourth Army was no outgrowth or faithful copy of the senior and better-known Eighth Route Army but a body with its own origins and history, and with original features that make it highly interesting for historians. This distinctiveness derived mainly from the background in the Three-Year War (1934-1937) of the Communist guerrillas left behind in the south who set up the army, but it also owed much to the unique political, military, and social environment that the army encountered in the lower Yangtze region, where it first joined battle with the Japanese. After the Wannan Incident of January 1941, in which its headquarters were destroyed, the New Fourth Army began to look increasingly like the Eighth Route Army, its more typically Maoist elder brother in the north. The Wannan Incident led to a radical reorganisation of its detachments and the definitive realignment of its politics. Thus transformed, the older New Fourth Army engages less for its own intrinsic and distinctive nature than as a division (subject only to circumstantial variation) of the general movement of Chinese communism at war. The Wannan Incident represented a turning-point and, in some respects, a decisive break in the army's development, and therefore forms a natural climax and finale to this study.