“The most impossible job on this earth,” was how its first holder, Trygve Lie, described it when he received his successor, Dag Hammarskjöld, at New York's Idlewild Airport on 9 April 1953. A further five decades have not made the role of the Secretary-General of the United Nations any easier, though the seven men who have held the function have exercised it in widely differing global political environments. Hammarskjöld, who inherited the position from the only Secretary-General who has ever resigned, did most to shape and define the institution, both by his own intellectual appreciation of its possibilities and by his conduct in office. As the seventh Secretary-General, Kofi Annan, the only other Nobel Peace laureate from that exclusive list, completes his tenure, it is instructive to examine how the role of the Secretary-General has evolved in the half-century since Dag Hammarskjöld made it his own.

The framers of the UN Charter used up ninety-six articles before they got around to defining the role of the Secretary-General, which took them five relatively brief ones – just over 300 words in total. These five articles gave the Secretary-General two distinct and seemingly unrelated functions: that of “chief administrative officer of the Organization” (Article 97) and that of an independent official whom the General Assembly and the Security Council could entrust with the task of carrying out certain unspecified (but implicitly political) functions (Article 98). Dag Hammarskjöld was the first UN Secretary-General to explicitly point to, and build upon, the qualitative difference this represented from the days of the League of Nations.