The Japanese forces were too few in number to permit a complete occupation of northern China. The invaders therefore concentrated on holding the cities and lines of communication. The complex pattern that resulted is shown as of 1940 in the above map which is based on Japanese military sources. Within the generally pacified area there were substantial pockets of resistance where guerilla forces and "bandits" of both Communist and Nationalist forces were active. Some resistance also came from groups designated by the Japanese as "purely local" bandits. The main concentration of regular Chinese guerilla forces were distributed along the southwest front. The principal northern center of communist power was outside the Japanese-controlled zone in the Sha'anxi-Gansu-Ningxia region with its capital at Yan'an. The net affect allowed Mao's forces to grow without attacks by the Nationalist because the Japanese forces lie between the two Chinese arch enemies.

Blue in Japanese controlled areas and red in Communist controlled areas.