UNITED NATIONS – Kofi Annan steps down as secretary-general at midnight today, leaving behind a global organization far more aggressively engaged in peacekeeping and fighting poverty – but struggling to restore its tarnished reputation.

Taking office six years after the collapse of the Soviet Union, Annan helped preside over a decade that saw the world unite against terrorism after the Sept. 11, 2001, attacks, then divide deeply over the U.S.-led war against Iraq which toppled Saddam Hussein.

At a Millennium Summit in September 2000, he spurred world leaders to adopt a blueprint to wage a global war on poverty and bring the United Nations into the 21st century.

Five years later, he called a follow-up summit to mark the U.N.’s 60th anniversary. Hoping to complete the bold changes, he sought to promote development, ensure international security and end human rights abuses.

Unlike the upbeat atmosphere at the dawn of the new millennium, the World Summit in 2005 took place after a year of almost daily attacks on the United Nations over allegations of corruption in the U.N. oil-for-food program in Iraq, bribery by U.N. purchasing officials, and widespread sex abuse by U.N. peacekeepers.

In what was considered a major summit achievement, world leaders pledged to protect civilians from genocide, war crimes and ethnic cleansing – but before stepping down earlier this month U.N. humanitarian chief Jan Egeland accused leaders of failure to translate their pledge into action, especially in Sudan’s Darfur region, Iraq and the Palestinian-Israeli conflict.

At a farewell news conference earlier this month, Annan said he considered his top achievements the promotion of human rights, fighting to close the gap between extreme poverty and immense wealth, and the U.N.’s campaign to fight infectious diseases.

Annan, 68, said he will maintain all those U.N. concerns – and many more – in his new life, likely to be divided between Switzerland and his native Ghana.

“You can take the man out of the U.N.,” Annan told one recent farewell party, “but you can’t take the U.N. out of the man.”