The Gang of Four's Zhang Chunqiao, himself, admitted that the most crucial factor in the Cultural Revolution was not the Red Guards or the Cultural Revolution Group or the "rebel worker" organisations, but the side on which the PLA stood. When the PLA local garrison supported Mao's radicals, they were able to take over the local government successfully, but if they were not cooperative, the seizures of power were unsuccessful. Violent clashes occurred in virtually all cities, according to one historian. In response to the Wuhan Incident, Mao and Jiang Qing began establishing a "workers' armed self-defence force", a "revolutionary armed force of mass character" to counter what he estimated as rightism in "75% of the PLA officer corps." Chongqing city, a center of arms manufacturing, was the site of ferocious armed clashes between the two factions, with one construction site in the city estimated to involve 10,000 combatants with tanks, mobile artillery, anti-aircraft guns and "virtually every kind of conventional weapon." Ten thousand artillery shells were fired in Chongqing during August 1967. Nationwide, a total of 18.77 million firearms, 14,828 artillery pieces, 2,719,545 grenades ended up in civilian hands and used in the course of "violent struggles" which mostly took place from 1967 to 1968; in the cities of Chongqing, Xiamen, and Changchun, tanks, armoured vehicles and even warships were deployed in combat.