several complaints before the United Nations Security Council charging that Rhodesian security forces were violating Zambia's sovereignty and territorial integrity with South African support. Tensions flared again when Zambian troops fired across the border and killed two Canadian tourists on the Rhodesian side of Victoria Falls in May 1973. The increasing prospect of war with Rhodesia posed several unique security dilemmas for the ZDF. Firstly, Zambia lacked the manpower or conventional hardware necessary to provide a suitable deterrent to a Rhodesian incursion. It also remained dependent on a relatively small pool of white senior officers and technical personnel. After 1967 Kaunda's government began replacing them with foreign officers on contract, ostensibly to minimise the potential for conflicts of loyalty. Between 1967 and 1970 the majority of officers in the ZDF were seconded from the British Army. In 1971, the ZDF was finally prepared to appoint its first black army and air force commanders. Due to the white community's close ties with Rhodesia and South Africa, white Zambians were subsequently barred from voluntary enlistment and granted a blanket exemption from conscription. Around September 1967, Kaunda made two requests to the United States for equipment for the Zambian Army, including long-range missile systems, but was rebuffed. More successful were Zambia's attempts to acquire its first combat aircraft, a number of Aermacchi MB-326 and SIAI-Marchetti SF.260s sourced from Italy; the first black Zambian Air Force pilots were trained by Italian instructors between 1966 and 1969. Italy also sold the ZDF helicopters and towed artillery. Involvement in regional conflicts, 1968–80 During the 1970s, Zambia began providing sanctuary for a number of revolutionary and militant political movements dedicated to overthrowing colonial and white minority rule elsewhere on the African continent. Guerrilla armies based in exile in Zambia included the People's Liberation Army of Namibia (PLAN) and the Zimbabwe People's Revolutionary Army (ZIPRA). These movements ultimately embroiled the ZDF in their own internal power struggles as well as direct clashes with foreign troops carrying out preemptive strikes. In 1968, the ZDF skirmished with Portuguese troops which had pursued a number of Angolan or Mozambican insurgents into Zambia. In September 1975, Zambian troops became locked in a firefight with insurgents of the Zimbabwe African National Liberation Army (ZANLA). The ZDF killed eleven ZANLA insurgents and later expelled that movement from Zambian soil. A year later, nearly two thousand disaffected PLAN insurgents in Zambia launched a mutiny which