UN Secretary General Kofi Annan retires at the end of December. He was the seventh secretary general, serving for two terms of five years each, starting on 1 January 1997.
BBC News website world affairs correspondent Paul Reynolds looks back at his time in office.
Kofi Annan's time in office was marked above all by the war in Iraq and the existential question for the UN about how far it can act on behalf of all states.
It was a question for which he had his own answer - certainly the UN should act on behalf of not just the major powers but all states.
But his answer did not in the end impress the Republican leadership in the United States and he is leaving office with the relationship tense and unresolved.
He holds to his view that the war in Iraq was "illegal" (adding recently that Iraq is in a "civil war", language rejected by the Bush administration) and Washington remains sceptical about the centrality of the UN in a crisis.
In one of his last speeches, at the Truman Library in Missouri, he referred to his "difficult but exhilarating role of secretary general". President Harry Truman signed the UN Charter on behalf of the United States.
And he appealed to Americans not to go down a unilateral path.
"You Americans did so much, in the last century, to build an effective multilateral system, with the United Nations at its heart," he said. "Do you need it less today, and does it need you less, than 60 years ago?
"Surely not. More than ever today Americans, like the rest of humanity, need a functioning global system through which the world's peoples can face global challenges together.
"And in order to function, the system still cries out for far-sighted American leadership, in the Truman tradition.
"I hope and pray that the American leaders of today, and tomorrow, will provide it."
It was said more in sorrow than in anger. Kofi Annan's style was never to show anger.
He did try to change the UN in order to make it more responsive.
Darfur is a good test of the UN's new powers - so far, it cannot be said to have succeeded
He set up a high-level international panel to make recommendations and some of these were agreed - the most important, perhaps, being the acceptance by member states that they have a "responsibility to protect" their citizens.
This implies that others have a right of intervention and is a significant move away from the old rule of "non-interference in the internal affairs" of another state.
Another reform was the establishment of a new Human Rights Council to take over from the discredited Human Rights Commission.
However, the long-term value of the new council remains to be seen.
The UN now has greater power to act. Whether it will do so remains the key issue, as Darfur bears witness.
Darfur is a good test of the UN's new powers - so far, it cannot be said to have succeeded.
It is worth recalling that before the Iraq crisis, Kofi Annan was not only popular in Washington but worldwide. He and the UN were jointly awarded the Nobel Peace prize in 2001 "for their work for a better organised and more peaceful world".
"I think that Kofi Annan has been a very fine secretary general through an extraordinarily turbulent period. Not everything has gone right, but we were lucky to have him," said Lord David Hannay, a former British UN ambassador and member of Mr Annan's reform panel.
"The Security Council was paralysed over Iraq and although many wish he had been more forthright at the time, it would have made no difference.
"It illustrates that while the secretary general might have great influence he has little power. Trying to attach personal responsibility to him is a major failure to understand how the system works."
Lord Hannay said Mr Annan had done all he could to resolve the crisis in Darfur, where at least 200,000 people have died and some 2.5 million have lost their homes in three years of fighting.
"Blame does not fall on him but on the obduracy of the Sudanese government and the divided councils in the UN.
"He deserves a lot of credit for his ambition in going for reform. It was worth doing and the UN has a new potential but of course there can also be false dawns."
One dark period for him personally was the inquiry into the oil-for-food programme under which Saddam Hussein's Iraq was allowed to sell oil in exchange for humanitarian goods.
He called these "painful moments". It turned out that the programme was also a mechanism for Iraq to enrich itself in dollars and influence, by selling only to favoured clients and then demanding "commission" on the sales.
Kofi Annan was cleared of personal blame in a report in 2005 by the former head of the US Federal Reserve, Paul Volcker, but the corruption reflected badly on his administrative oversight.
And the role his son Kojo played for a Swiss firm that monitored the oil-for-food transactions came under scrutiny.
No evidence was found that the secretary general had used his influence to help his son but the report concluded that he did not exercise enough scrutiny to avoid a potential conflict of interest.
Mr Annan said he had been exonerated. Mr Volcker said he had not.
Despite calls for his resignation, Kofi Annan survived.
The resignation cries came notably from the right in the United States. Senator Norm Coleman led the charge and to this day remains hostile, taking aim at Mr Annan recently when commenting on the election of the South Korean Ban Ki-moon as the new secretary general:
"I am hopeful that a new secretary general can aggressively implement reforms that are needed to make the UN an effective and transparent organisation," said Senator Coleman.
The end of the scandal-ridden reign of Kofi Annan presents a new opportunity to move towards the reforms essential for restoring the UN's credibility."
His record has also been undermined by references to his failures while in his previous job as under secretary for peacekeeping during which the Srebrenica and Rwanda massacres took place.
All this has led to a critical valedictory poem in the London-based Spectator magazine by Norman Bissett, the opening line of which reads:
"A limp soft-soaper, he wouldn't say Boo to a goose."
For all his personal charm and moderate manners, Kofi Annan was a man who attracted strong opinions.
Nobody doing his job and in his time could probably have avoided that.