Dag Hammarskjold (Sweden, 1953-1961, died in plane crash) 4

Effectively defined and expanded the office and powers of the secretary general. Much of tenure was consumed with the unstable situation in Africa as the effects of decolonization were felt. In addition, he negotiated the release of US pilots captured by the Chinese during the Korean War, established the UN Emergency Force and intervened in the Suez Canal crisis. Hammarskjold was a skilled diplomat and able to wield the powers of his office with some skill, something several of his successors have lacked. His death in a plane crash under questionable circumstances in Africa ended the career of the most effective, and most balanced, Secretary General of the UN.