Annan died Saturday after an unspecified short illness, according to a statement from his family and the Kofi Annan Foundation. He was 80.

Current UN Secretary-General Antonio Guterres said Annan was a guiding force for good. “In many ways, Kofi Annan was the United Nations,” he said. “He rose through the ranks to lead the organization into the new millennium with matchless dignity and determination.”

Annan devoted almost his entire working life to the UN, navigating through multiple wars in the Middle East, the Balkan breakup, African genocides and a raft of other crises over a career that spanned more than five decades.

He was the co-recipient, along with the UN, of the 2001 Nobel Peace Prize, to recognize “work for a better organized and more peaceful world.” His opposition to the Iraq War in 2003 endeared him to antiwar groups and drew sharp criticism from U.S. conservatives, including John Bolton, the former U.S. ambassador to the UN who became national security adviser to President Donald Trump.

Admiration, Criticism

Although broadly admired as a bureaucratic reformer and quiet insider, Annan was often assailed as ineffective. He was criticized for his handling of UN peacekeeping operations at the time of the genocide of Rwandan Tutsis in 1994 and the killing of Muslims from the Bosnian town of Srebrenica the following year. His reputation was tainted further by a corruption scandal that touched his family and a failure to help resolve the Syrian crisis in 2012, when it was in its infancy.

“A lot of his time as secretary-general was devoted to redeeming both the UN’s battered reputation and his own,” said Richard Gowan, a fellow at the European Council on Foreign Relations. “Annan and his advisers managed to nurse UN operations back to life, and launch new blue missions in trouble spots like Congo and Liberia. If Annan hadn’t pushed the UN back into peacekeeping in Africa, the organization would be even less credible in global security than it is today.”

Following his two terms as secretary-general, Annan became a member of the Elders, an elite group of retired liberal leaders, including Nelson Mandela and Jimmy Carter, partly financed by Richard Branson to resolve conflicts around the world through informal counsel.

In February 2012, Annan was appointed the first UN special envoy to Syria in an attempt to end the civil war that had broken out the previous year. He resigned six months later, citing intransigence of both government and rebels. He called for UN peacekeeping troops to be deployed, but world powers could not agree to such a plan.

In his 2012 memoir, “Interventions: A Life in War and Peace,” Annan wrote that Syrian President Bashar al-Assad’s response to the popular uprising “confirmed my more troubling suspicion that he was a man beholden to a small group of Alawite security officers and willing to employ any means to retain power.”

Nonetheless, Annan maintained his stature in world diplomacy and in 2016 was appointed to head a UN commission to investigate the Rohingya crisis in Myanmar.

Leaders React

Tributes poured in Saturday from world leaders expressing their sadness at the news of Annan’s death.

Ghanaian President Nana Okufo-Addo said on Twitter that Ghanaian flags would fly at half-staff for a week starting Monday. He called Annan “an ardent believer in the capacity of the Ghanaian to chart his or her own course onto the path of progress and prosperity.”

U.K. Prime Minister Theresa May said of Annan on Twitter that as “a great leader and reformer of the UN, he made a huge contribution to making the world he has left a better place than the one he was born into.”

French President Emmanuel Macron said on Twitter, “France pays homage to him. We will never forget his calm and determined demeanor, nor the force of his efforts.”

Russian President Vladimir Putin expressed condolences in a message to Guterres, according to an emailed statement from the Kremlin. “I sincerely admired his wisdom and courage, and the ability to make informed decisions even in the most difficult, critical situations,” Putin wrote.

Gro Harlem Brundtland, deputy chairwoman of the Elders, said the group was “devastated” by his death. “Kofi was a strong and inspiring presence to us all, and the Elders would not be where it is today without his leadership,” she said.

South African Archbishop Emeritus Desmond Tutu, whom Annan succeeded as chairman of the Elders in 2013, said in a statement, “We give great thanks to God for Kofi Annan, an outstanding human being who represented our continent and the world with enormous graciousness, integrity and distinction.”

South African President Cyril Ramaphosa paid tribute to Annan in an emailed statement as “a great leader and diplomat extraordinaire” who had advanced the African agenda within the United Nations and had “flown the flag for peace” around the world.

Gold Coast

Annan was born on April 8, 1938, in Kumasi, Gold Coast, which later changed its name to Ghana. He attended an elite boarding school in Cape Town before studying economics at the Kumasi College of Science and Technology. He received a Ford Foundation grant to complete his studies at Macalester College in St. Paul, Minnesota.

After graduation in 1962, Annan joined the World Health Organization, a UN agency, as a budget officer before leaving to earn a master’s degree in management at the Massachusetts Institute of Technology in 1971.

Annan returned to the UN as head of personnel for the UN High Commission for Refugees in Geneva before moving to New York to become an assistant secretary-general. In 1992, after Secretary-General Boutros Boutros-Ghali established the Department of Peacekeeping Operations, Annan became its head.

In January 1994, Annan failed to authorize UN peacekeeping troops to seize a Hutu arms cache to preempt plans for mass killings in the capital. Annan ordered the local commander not to take any action and failed to keep the Security Council informed even as the genocide had started.

Accepts Responsibility

In his memoir, Annan accepts responsibility, and writes that the UN “had no genuine, deep expertise on the country.”

Months after the Rwandan massacre, UN troops stood by as more than 8,000 Muslim men and boys were killed by Serbian paramilitary units in the town of Srebrenica. Annan later apologized.

Annan was appointed secretary-general in 1996 after the U.S. said it would veto a second term for incumbent Boutros-Ghali of Egypt.

Annan’s rise to head the UN was “a moment of joy and pride for me, all of us, his mates, the school, Ghana and sub-Saharan Africa,” said Nana Nsaful, 76, a school friend.

During the buildup to the 2003 invasion of Iraq, Annan called on the U.S. and the U.K. not to attack without the support of the UN. He later called the invasion illegal.

Toward the end of his tenure, Annan became embroiled in charges that his son, Kojo Annan, had received payments from the Geneva-based Cotecna Inspection SA, which had won a lucrative contract under the UN’s oil-for-food program for Iraq.

Volcker’s Inquiry

An inquiry led by former U.S. Federal Reserve Chairman Paul Volcker found in September 2005 that Annan knew about Saddam Hussein’s corruption of the almost $70 billion program and did little to stop the illegal activity.

Annan “maintained a passive attitude and made no serious effort to curtail the surcharge scheme,” the report said. His response to the smuggling “reveals a pattern of inaction and inadequate disclosure.”

He finished his term at the end of 2006, succeeded by Ban Ki-moon of South Korea.

After the UN, Annan, set up the Kofi Annan Foundation, which works to promote good global governance and peace.

In 1984, Annan married Nane Lagergren, a Swedish lawyer at the UN and the niece of Raoul Wallenberg, a Swedish diplomat who saved thousands of Jews in Nazi-occupied Hungary. His son, Kojo, and daughter, Ama, were from an earlier marriage. Nane Annan has a daughter, Nina Cronstedt de Groot, from a previous marriage.