FEW US diplomats had the breadth, depth or length of service of Richard Holbrooke, who wrote part of the Pentagon Papers, and was the architect of the 1995 Bosnia peace accords and served as President Barack Obama's special envoy to Pakistan and Afghanistan.

Holbrooke's unexpected death on Monday at 69, following surgery for a tear in his aorta, marked the end of a storied career. He served through defining eras in US diplomacy, witnessing the end of European colonialism and the Cold War and the rise of international terrorism as the greatest threat to America.

Calling Holbrooke "a true giant of American foreign policy", Obama paid homage to his crisis expert as "a truly unique figure who will be remembered for his tireless diplomacy, love of country and pursuit of peace".

Holbrooke deserves credit for much of the hard-won progress in Afghanistan and Pakistan, the president said.

Mike Mullen, chairperson of the Joint Chiefs of Staff, said Holbrooke's presence would be especially missed this week as the Obama administration finishes its review of the Afghan war.

Mullen said Holbrooke helped write and "deeply believed in" the war strategy.

"That we have been making steady progress in this war is due in no small measure to Richard's tireless efforts and dedication," Mullen said. "I know he would want our work to continue unabated. And I know we will all feel his bully presence in the room as we do so."

Holbrooke served under every Democratic president since John F. Kennedy. He brought a lion's appetite for difficult work, from Indochina and the Pacific to Europe, Africa and, in his last incarnation, South Asia.

Supremely self-confident, brash and instantly dismissive of critics, Holbrooke entered the foreign service in the early 1960s at the height of what critics called the State Department's "pale, male and Yale" phase.

It was a time when the dictum of former Secretary of State Henry Stimson - "Gentlemen, don't read each other's mail" - still rang through the corridors of Foggy Bottom, the State Department's Washington neighborhood.

At the time of his death, Holbrooke - an Ivy League graduate of Brown University, not Yale - was serving a vastly different agency. The State Department in recent years has been led by an African-American man and three women, one of them African-American.

And, quite far from Stimson's admonition, the department instructed its diplomats to seek out personal information about foreign leaders and politicians, according to leaked classified documents released by the WikiLeaks website. He is survived by his wife, author Kati Marton, and two sons from a previous marriage.