In July 1940, Peng was given overall command of the largest communist operation of the anti-Japanese war, the Hundred Regiments Offensive, when 200,000 regular troops from the Eighth Route Army participated in the operation and were supported by 200,000 irregular communist guerrillas. From August 20 to October 5, 1940, communist forces destroyed large numbers of bridges, tunnels, and railroad tracks in Japanese-occupied China and inflicted relatively heavy Japanese casualties. From October 6 to December 5, the Japanese counterattacked, and the communists mostly repelled the counterattack successfully. Peng's operation was successful in disrupting Japanese communication lines and logistics networks, which were not fully restored until 1942, but the communists suffered heavy losses, In communist sources, the Japanese casualties have two figures, one of which is 20,645 and the other 12,645. Foreign sources give figures of 20,900. In early 1941, the Japanese began a large-scale effort to drive Peng from his base in Taihangshan, and Peng relocated closer to the communist base in Yan'an in late 1941.