Query: When did European powers grant independence to their colonies in Africa?
Context: The Herero Chief's Council submitted a number of petitions to the UN calling for it to grant Namibia independence during the 1950s. During the 1960s, when European powers granted independence to their colonies and trust territories in Africa, pressure mounted on South Africa to do so in Namibia. In 1966 the International Court of Justice dismissed a complaint brought by Ethiopia and Liberia against South Africa's continued presence in the territory, but the U.N. General Assembly subsequently revoked South Africa's mandate, while in 1971 the International Court of Justice issued an "advisory opinion" declaring South Africa's continued administration to be illegal.