The 'Hundred Regiments Offensive' was a Chinese major campaign by the communist Red Army, under the command of Peng Te-huai, against the Japanese army in the north-central region of China (20 August/5 December 1940).

In 1939/40 the Japanese forces in China had launched more than 109 small campaigns each involving about 1,000 combatants, and 10 large campaigns each involving some 10,000 men or more in their efforts to destroy the communist guerrilla forces in the Hebei and Shandong plains. In addition, Wang Ching-wei’s anti-communist puppet government had undertaken its own offensive against the communist guerrillas.

There was a general sentiment among the anti-Japanese resistance forces of China, particularly in the Kuomintang, that the communists were not contributing enough to the Chinese war effort, and were interested only in expanding their power base. It was as a result of these circumstances that the communists planned a major offensive to prove that they were helping the war effort, and so improve relations with the Kuomintang.

General Hayao Tada’s Northern China Area Army estimated the strength of communist regulars to be about 88,000 in December 1939, but two years later revised its estimate to 140,000. On the eve of the battle the communist forces had some 400,000 men distributed in 115 regiments. The extraordinary success and expansion of Chu Teh’s 8^th Route Army against the Japanese had its commander and, indeed, the rest of the communist politico-military leadership hoping that the communist forces could engage the Japanese army and win. Mao Tse-tung argued that the war against Japan would be protracted, and that communist strategy should emphasise guerrilla warfare, political mobilisation and the building up of base areas.

Nevertheless, by 1940 the growth of the communist military strength was so great that Chu Teh ordered a co-ordinated offensive by most of the communist regular units (46 regiments of Lin Piao’s 115^th Division, 47 of the 129^th Division and 22 of the 120^th Division) against the Japanese-held cities and the railway lines linking them.

From 20 August to 10 September the communist forces attacked the railway line that separated the communist base areas, chiefly those from Dezhou to Shijiazhuang in Hebei, Shijiazhuang to Taiyuan in central Shanxi, and Taiyuan to Datong in northern Shanxi. They succeeded in blowing up bridges and tunnels and ripping up track, and went on for the rest of September to tackle the Japanese garrisons frontally, taking very heavy losses (22,000 regulars compared to Japanese losses of between 3,000 and 20,900 men according to source). In all, about 600 miles (965 km) of railway track were destroyed and the Chingching coal mine, which was important to the Japanese war industry, was rendered inoperative for six months.

This was the greatest victory fought and won by the communists during World War II. However, from October to December the Japanese responded in force, reasserting control of railway lines and conducting aggressive clearance operations in the rural areas around them. When General Yasuji Okamura took command of the Northern China Area Army in the summer, his response to the 'Hundred Regiments Offensive', in which the Japanese-led forces had taken casualties of 46,000 (including 20,900 Japanese) men to the communists' 22,000 men, was the 'Sanko' (three alls) campaign, as a result of which the population of the communist base areas dropped dramatically and communist operations were severely limited, with the communist forces reduced to 300,000 men. Communist control was also reduced to 10 out of 437 counties in the northern part of China.

Mao used the subsequent 'rectification campaign' to reassert his personal authority over the party and over military strategy, and this meant the abandonment of any serious communist challenge to the Japanese position in the northern part of China for the rest of the war. Henceforward, therefore, the communists engage the Japanese only in guerrilla warfare and concentrate on rebuilding their own foothold in the northern part of China. Mao criticised Peng for revealing the strength of the communist forces to the Kuomintang.