From the 1960s to the 1990s, South Africa pursued research into weapons of mass destruction, including nuclear, biological, and chemical weapons under the apartheid government. Six nuclear weapons were assembled. South African strategy was, if political and military instability in Southern Africa became unmanageable, to conduct a nuclear weapon test in a location such as the Kalahari desert, where an underground testing site had been prepared, to demonstrate its capability and resolve—and thereby highlight the peril of intensified conflict in the region—and then invite a larger power such as the United States to intervene. Before the anticipated changeover to a majority-elected African National Congress–led government in the 1990s, the South African government dismantled all of its nuclear weapons, the first state in the world which voluntarily gave up all nuclear arms it had developed itself. The country has been a signatory of the Biological Weapons Convention since 1975, the Treaty on the Non-Proliferation of Nuclear Weapons since 1991, and the Chemical Weapons Convention since 1995. In February 2019, South Africa ratified the Treaty on the Prohibition of Nuclear Weapons, becoming the first country to have had nuclear weapons, disarmed them and gone on to sign the treaty. Nuclear weapons The Republic of South Africa's ambitions to develop nuclear weapons began in 1948 after giving commission to South African Atomic Energy Corporation (SAAEC), the forerunner corporation to oversee the nation's uranium mining and industrial trade. In 1957, South Africa reached an understanding with the United States after signing a 50-year collaboration under the U.S.-sanctioned programme, Atoms for Peace. The treaty concluded the South African acquisition of a single nuclear research reactor and an accompanying supply of highly enriched uranium (HEU) fuel, located in Pelindaba. In 1965, the U.S. subsidiary, the Allis-Chalmers Corporation, delivered the 20 MW research nuclear reactor, SAFARI-1, along with ~90% HEU fuel to South African nuclear authority. In 1967, South Africa decided to pursue plutonium capability and constructed its own reactor, SAFARI-2 reactor also at Pelindaba, that went critical using 606 kg of 2% enriched uranium fuel, and 5.4 tonnes of heavy water, both supplied by the United States. The SAFARI-2 reactor was intended to be moderated by heavy water, fuelled by natural uranium while the reactor's cooling system used molten sodium. In 1969, the project was abandoned by the South African government because the reactor was draining resources from the uranium enrichment program that had begun in