In October, 1937, an announcement was made that Red Army soldiers active in the eight provinces in southern China — those who did not embark on the Long March would be part of the New Fourth Army. The New Fourth Army was established on December 25, 1937 in Hankou, moving to Nanchang on January 6, 1938, when the detachments began marching to the battlefront. At the beginning, the New Fourth Army had four detachments and one task force battalion and numbered roughly ten thousand. Later the army moved to Anhui province. Ye Ting was the army commander, Xiang Ying the deputy army commander.
It was in theory a united front against Japan but in practice there was friction between Nationalist and Communist Forces, which intensified in the fall of 1940, culminating in the New Fourth Army Incident with a full fledged battle between the New Fourth Army and KMT National Revolutionary Army forces. Up until that point, most of the battles had been skirmishes. The army was fully reorganised after the incident and remained in active combat until the end of the war.