While his identity was known to a small group of colleagues and officials, to the public he was known - if he was known at all - simply as "Hank" or "Henry".
Now, after decades undercover, Henry "Hank" Crumpton has stepped from the shadows to take the helm of the US State Department's counter-terrorism section. With the job comes the title of ambassador.
In the aftermath of the 11 September attacks, Mr Crumpton was appointed to head the US covert effort in Afghanistan. He was responsible for drafting a strategy that deployed intelligence officers and special forces to work in co-ordination with local Afghan groups to drive out the Taliban.
"Hank was a tough, focused, brave operator and an excellent organiser. His work was invaluable," General Tommy Franks, the retired head of Central Command, told The Washington Post.
In the 9/11 Commission's report, he was referred to as Henry. In Bob Woodward's book Bush at War, he is known as Hank. In his own words - contributing two chapters to a forthcoming book on challenges faced by the US intelligence services - he stresses how important economic and social factors became in persuading Afghans to join the effort to oust the Taliban. He said that many Afghans fought for tribal honour as well as political gain.
"US power is usually measured in terms of kinetic strength but the power of empathy, honour, prestige, hope and material self-interest can complement raw strength and produce a more effective, more enduring victory," he writes in Transforming US Intelligence, edited by Jennifer Sims. Mr Crumpton, from Georgia, also advocates relying on local forces and noted the advice of Lawrence of Arabia in the First World War. "Do not try to do too much with your own hands. Better the Arabs to do it tolerably than that you do it perfectly ... Also under the very odd conditions of Arabia your practical work will not be as good, perhaps, as you think it is." In an interview with the Post, Mr Crumpton, who was sworn in as co-ordinator for counter-terrorism last month, revealed that he had wanted to be a CIA operative since he was a boy. As a child he wrote to the CIA and the agency wrote back. "They responded - on letterhead. In a rural community in Georgia, to get a letter from the CIA, that was pretty cool."
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