Europeans resident in Zambia in 1964, and they remained of disproportionate economic significance. Post-independence Kaunda's endorsement of Patriotic Front guerrillas conducting raids into neighbouring (Southern) Rhodesia resulted in political tension and a militarisation of the border, leading to its closure in 1973. The Kariba hydroelectric station on the Zambezi River provided sufficient capacity to satisfy the country's requirements for electricity, despite Rhodesian management. On 3 September 1978, a civilian airliner, Air Rhodesia Flight 825, was shot down near Kariba by the Zimbabwe People's Revolutionary Army (ZIPRA). 18 people, including children, survived the crash only for most of them to be shot by militants of the Zimbabwe African People's Union (ZAPU) led by Joshua Nkomo. Rhodesia responded with Operation Gatling, an attack on Nkomo's guerilla bases in Zambia, in particular, his military headquarters just outside Lusaka; this raid became known as the Green Leader Raid. On the same day, two more bases in Zambia were attacked using air power and elite paratroops and helicopter-borne troops. A railway (TAZARA – Tanzania Zambia Railways) to the Tanzanian port of Dar es Salaam, completed in 1975 with Chinese assistance, reduced Zambian dependence on railway lines south to South Africa and west through an increasingly troubled Portuguese Angola. Until the completion of the railway, Zambia's major artery for imports and the critical export of copper was along the TanZam Road, running from Zambia to the port cities in Tanzania. The Tazama oil pipeline was also built from Dar es Salaam to Ndola in Zambia. By the late 1970s, Mozambique and Angola had attained independence from Portugal. Rhodesia's predominantly white government, which issued a Unilateral Declaration of Independence in 1965, accepted majority rule under the Lancaster House Agreement in 1979. Civil strife in both Portuguese colonies and a mounting Namibian War of Independence resulted in an influx of refugees and compounded transportation issues. The Benguela railway, which extended west through Angola, was essentially closed to Zambian traffic by the late 1970s. Zambia's support for anti-apartheid movements such as the African National Congress (ANC) also created security problems as the South African Defence Force struck at dissident targets during external raids. Economic troubles In the mid-1970s, the price of copper, Zambia's principal export, suffered a severe decline worldwide. In Zambia's situation, the cost of transporting the copper great distances to the market was an additional strain. Zambia turned to foreign and international lenders for relief, but, as