more often crippled than destroyed outright. Vietnam War During the Vietnam War, both 'regular' NVA and Viet Cong forces used AT mines. These were of Soviet, Chinese or local manufacture. Anti-tank mines were also used extensively in Cambodia and along the Thai border, planted by Pol Pot's Maoist guerrillas and the Vietnamese army, which invaded Cambodia in 1979 to topple the Khmer Rouge. Millions of these mines remain in the area, despite clearing efforts. It is estimated that they cause hundreds of deaths annually. Southern Africa Conflict in southern Africa since the 1960s have often involved Soviet, United States or South African supported irregular armies or fighters engaged in guerrilla warfare. What makes these conflicts significant to the study of anti-tank mines is that they featured the widespread use of these mines in situations other than conventional warfare (or static minefields) and also saw the development of effective mine resistant vehicles. As a result, both Angola and Mozambique are littered with such devices to this day (as with Cambodia). In the Angolan Civil War or South African Border War that covered vast sparsely populated area of southern Angola and northern Namibia, it was easy for small groups to infiltrate and lay their mines on roads before escaping again often undetected. The anti-tank mines were most often placed on public roads used by civilian and military vehicles and had a great psychological effect. Mines were often laid in complex arrangements. One tactic was to lay multiple mines on top of each other to increase the blast effect. Another common tactic was to link together several mines placed within a few metres of each other, so that all would detonate when any one was triggered. It was because of this threat that some of the first successful mine protected vehicles were developed by South African military and police forces. Chief amongst these were the Buffel and Casspir armoured personnel carriers and Ratel armoured fighting vehicle. They employed v-shaped hulls that deflected the blast force away from occupants. In most cases occupants survived anti-tank mine detonations with only minor injuries. The vehicles themselves could often be repaired by replacing the wheels or some drive train components that were designed to be modular and replaceable for exactly this reason. Most countries involved in Middle Eastern peace keeping missions deploy modern developments of these vehicles like the RG-31 (Canada, United Arab Emirates, United States) and