South Africa developed nuclear weapons due to the threat to its security posed by the presence of large numbers of Cuban troops in Angola and Mozambique. In November 1975, Cuba poured more than 65,000 troops into Angola in one of the fastest military mobilizations in history. On November 10, 1975, Cuban forces defeated the National Liberation Front of Angola (FNLA) in the Battle of Quifangondo. On November 25, 1975, as the South African Defence Force (SADF) tried to cross a bridge, Cubans hidden along the banks of the river attacked, destroying seven armored cars and killing upwards of 90 enemy soldiers. On March 27, 1976, the last South African troops withdrew from Angola. In September 1977, 12 MiG-21s conducted strafing flights over Puerto Plata in Dominican Republic to warn then president Joaquín Balaguer against intercepting Cuban warships headed to or returning from Angola. In 1988, Cuba returned to Angola with a vengeance. The crisis began in 1987 with an assault by Soviet-equipped national army troops against the pro-Western rebel movement UNITA in southeastern Angola. Soon, the SADF invaded to support the beleaguered US-backed faction and the Angolan offensive stalled. Cuba reinforced its African ally with 55,000 troops, tanks, artillery and MiG-23s, prompting Pretoria to call up 140,000 reservists. In June 1988, SADF armor and artillery engaged FAPLA-Cuban forces at Techipa, killing 290 Angolans and 10 Cubans. In retaliation, Cuban warplanes hammered South African troops. However, both sides quickly pulled back to avoid an escalation of hostilities. The Battle of Cuito Cuanavale stalemated, and a peace treaty was signed in September 1988. Within two years, the Cold War was over and Cuba's foreign policy shifted away from military intervention.