Renowned secretary-general of the United Nations Dag Hammarskjöld dies in a plane crash on this day. Hammarskjöld, the son of a former Swedish prime minister, was elected to the top U.N. post in 1953 and in 1957 was unanimously re-elected. During his second term, he initiated and directed the United Nation's vigorous role in the Belgian Congo, which included the deployment of peacekeeping troops in 1960. He was on his fourth mission to the central African country when his plane crashed in Northern Rhodesia, now Zambia. An influential force for peace at the United Nations and around the world, he was posthumously awarded the 1961 Nobel Peace Prize.