United Nations Security Council resolution 591, adopted unanimously on 28 November 1986, after recalling resolutions 418 (1977), 421 (1977), 473 (1980) and 558 (1984), the Council strengthened the mandatory arms embargo against apartheid South Africa imposed by Resolution 418, and made it more comprehensive. Resolution 591 sought to clarify vague terms from previous resolutions on the topic.[1]