 Chinese militia who refused to switch their allegiance were often labelled "collaborators" and attacked by CPC forces.For example, the Red Army led by He Long attacked and wiped out a brigade of Chinese militia led by Zhang Yin-wu in Hebei in June 1939.Starting in 1940, open conflict between Nationalists and Communists became more frequent in the occupied areas outside of Japanese control, culminating in the New Fourth Army Incident in January 1941.