The most impossible job on earth" was how the first UN secretary-general, Trygve Lie, described the post to his successor, Dag Hammarskjold, in 1953. Time has not made the job any easier.
The framers of the UN Charter gave the secretary-general two distinct functions: "chief administrative officer of the organization" and also an independent official whom the General Assembly and Security Council can entrust with certain unspecified (but implicitly political) tasks. Each holder of the office must demonstrate whether he is more secretary than general.
Paradoxes abound. The secretary-general is expected to enjoy the backing of governments, especially the five permanent members of the Security Council, but be above partiality to any of them. He establishes his credentials by bureaucratic or diplomatic service, but, once elected, must transcend his past and serve as a voice of the world, even a "secular Pope."
The secretary-general is entrusted with assisting member states to make sound and well-informed decisions, which he is then obliged to execute, but he is also authorized to influence their work and even to propose actions that they should undertake. He administers a complex organization and serves as head of the UN agencies, but must exercise this role within budgetary and regulatory constraints imposed by the member governments.
True, the secretary-general has an unparalleled agenda-shaping authority. But he does not have the power to execute all his ideas, and he articulates a vision that only governments can fulfill. He moves the world, but he cannot direct it.
It was Hammarskjold who, at the height of the Cold War, first argued that an impartial civil servant could be "politically celibate" without being "politically virgin." The secretary-general could play a political role without losing his impartiality, provided he hewed faithfully to the charter and to international law.
With the Cold War's end, Kofi Annan has gone further than his predecessors in using the "bully pulpit" of his office. He boldly raised the question of the morality of intervention and the duty of the individual to follow his conscience, and he challenged member states to resolve the tensions between state sovereignty and their responsibility to protect the ordinary people.
Often, a secretary-general can raise an awkward question but not dictate the appropriate answer; Annan's historic speech to the General Assembly in 1999 on intervention set a thousand flowers blooming at think-tanks and among op-ed columnists, but it has not led to a single military intervention to protect the oppressed.
The UN is often seen embodying international legitimacy, yet the secretary-general's pronouncements often have less impact on the conduct of member states than the Pope's strictures on birth control.
The secretary-general knows that he can accomplish little without the support of members whose inaction on one issue or another he might otherwise want to denounce. He cannot afford to allow frustration on any one issue to affect his ability to elicit cooperation from governments on a range of others. Annan once made the point by citing an old Ghanaian proverb: "Never hit a man on the head when you have your fingers between his teeth."
Today's single-superpower world also means that the secretary-general must manage a relationship that is vital to the UN's survival without mortgaging his own integrity and independence. The insistent demands of some in the US that the UN prove its utility to the US -- demands that could not have been made in the same terms during the Cold War -- oblige a secretary-general to walk a tightrope between heeding US priorities and the preferences of the membership as a whole. Paradoxically, he can be most useful to the US when he demonstrates his independence from it.