of a 100mm tank gun round, the “Mortar Cannon” made by the FSA’s 16th Division that fires factory-made rounds, a compressed air cannon made by Ahrar al-Sham, the “Hellfire Cannon” and a number of multi-barrelled cannons such as the 4-barrelled “Quad Hell Cannon” and the 7-barrelled “Bureji” which is named after a Palestinian refugee camp in Gaza. Insurgency tactics Agents and sympathizers in place Insurgent organizations may recruit members of the government's civil and security forces to their cause or to have their own members join them. In addition to being able to provide intelligence and possibly provide direct and indirect aid, doing so allows insurgent members to gain military training and skills which they would not otherwise be able to access, these members may then serve as a cadre to train other insurgents, those who rise high enough may become agents of influence. Agitation Often grouped together with propaganda as agitprop, agitation is the use of agitators to stir up discontent both real and imagined with the regime and to propose a course of action to right these perceived wrongs. The traditional targets of agitators have been the shop floor, students' unions and the junior officer's mess halls of the military. Ambushes Ambushes have been used for as long as guerrilla warfare has been a tactic, and many guerrilla and insurgent groups have used ambushes as a way of defeating superior enemy forces with minimal risk to the insurgents. The ability of an insurgent force to launch an ambush against unsuspecting enemy forces and then withdraw in order to avoid engaging superior enemy reinforcements, or as a tactic of attrition to gradually wear down enemy forces by inflicting casualties and damaging morale, with minimal risk to the insurgents, makes ambushes a very useful tactic for guerrilla and insurgent forces. Guerrilla warfare was the primary tactic of the Viet Cong and North Vietnamese army when fighting against the United States and South Vietnam during the Vietnam War, as the thick jungle and rural farmland provided ideal cover for such activities. Ambushes were the most common tactic, with several different types. The terrain for the ambush had to meet strict criteria, allowing for the provision of concealment from both ground or air, to allow the ambush force to deploy, encircle and divide the enemy, the positioning of heavy weapons emplacements in kill zones to provide sustained fire, to enable the ambush