At the Johnson White House, he wrote one volume of the Pentagon Papers, an internal government study of U.S. involvement in Vietnam that was completed in 1967.
The study, leaked in 1971 by a former Defense Department aide, had many damaging revelations, including a memo that stated the reason for fighting in Vietnam was based far more on preserving U.S. prestige than preventing communism or helping the Vietnamese.
After stints in and out of government — including as Peace Corps director in Morocco, editing positions at Foreign Policy and Newsweek magazines and adviser to Jimmy Carter's presidential campaign, Holbrooke became assistant secretary of state for Asian affairs from 1977-81. He then shifted back to private life — and the financial world, at Lehman Brothers.
A lifelong Democrat, he returned to public service when Bill Clinton took the White House in 1993. Holbrooke was U.S. ambassador to Germany from 1993 to 1994 and then assistant secretary of state for European affairs.
"He could always be counted on for his imagination, dedication and forcefulness," Clinton-era Secretary of State Madeleine Albright said Monday.
One of his signature achievements was brokering the Dayton Peace Accords that ended the war in Bosnia.
Holbrooke's efforts would later lead to controversy when wartime Bosnian Serb leader Radovan Karadzic told a war crimes tribunal in 2009 that Holbrooke had promised him immunity in return for leaving politics. Holbrooke denied it.
Holbrooke left the State Department in 1996 to take a Wall Street job with Credit Suisse First Boston, but was never far from the diplomatic fray, serving as a private citizen as a special envoy to Cyprus and then the Balkans.
In 1998, he negotiated an agreement with Yugoslav President Slobodan Milosevic to withdraw Yugoslav forces from Kosovo, where they were accused of conducting an ethnic cleansing campaign.
"I make no apologies for negotiating with Milosevic and even worse people, provided one doesn't lose one's point of view," he said later.
When the deal fell apart, Holbrooke went to Belgrade to deliver the final ultimatum to Milosevic to leave Kosovo or face NATO airstrikes, which ultimately rained down on the capital.
Holbrooke returned to public service in 1999, becoming U.S. ambassador to the United Nations.
With his long-standing ties to Bill Clinton and Hillary Rodham Clinton, Holbrooke was a strong supporter of her 2008 bid for the White House. He had been considered a favorite to become secretary of state if she had won.
"Richard Holbrooke saved lives, secured peace and restored hope for countless people around the world," Bill Clinton said in a statement. Hillary Clinton called him one of America's "fiercest champions and most dedicated public servants."
When her presidential campaign ran out of steam, Holbrooke began reaching out to Obama.
Reflecting on his role as Obama's special envoy, Holbrooke wrote in The Washington Post in March 2008 that "the conflict in Afghanistan will be far more costly and much, much longer than Americans realize. This war, already in its seventh year, will eventually become the longest in American history, surpassing even Vietnam."
Gen. David H. Petraeus, commander of U.S. and NATO forces in Afghanistan, called Holbrooke "our diplomatic wingman" and said he was "a great American and a good friend."
Afghan President Hamid Karzai called Holbrooke's death "a big loss for the American people." In neighboring Pakistan, President Asif Ali Zardari said: "His services will be long remembered. The best tribute to him is to reiterate our resolve to root out extremism and usher in peace."