It was classic Gates: droll, attentive to timing, a little self-deprecating, acutely self-aware. It was also revealing. Gates is a careful, restrained player who wields his power with quiet but ruthless efficiency--as he did on Feb. 1, when he fired the military officer overseeing the Pentagon's new F-35 stealth-fighter-jet program for cost overruns and technical failures and punished Lockheed Martin by withholding $615 million in fees. Lots of defense contractors and program managers underachieve, yet they almost always get away with it. Not under Gates.

Like his fellow Cold War survivor the Doomsday Plane, Gates has come to embody power, control and an astonishing longevity. Just 5 ft. 8 in., with small hands and feet, the demure 66-year-old Kansan has outlasted seven Presidents as well as most of his fellow bureaucrats and policymakers. He's the only entry-level CIA analyst to rise to the top job, director of central intelligence. And he's the only Secretary of Defense ever to be asked to stay on in a rival party's Administration. He has thrived through a combination of endurance, pragmatism and bureaucratic savvy. And during the past year, on issue after issue--Pentagon reform, missile defense, Afghanistan and now the Pentagon's move to repeal the "Don't ask, don't tell" policy on gays in the military--Gates has become the most important player in the Obama war Cabinet. It's a remarkable feat, considering that he's the only Republican on the Democratic national-security team.

"Whatever Gates chooses to take a position on, Gates is the single most influential guy," says Leslie Gelb, the president emeritus of the Council on Foreign Relations and a skeptic of the Administration's strategy in Afghanistan. Gelb points out that in early December, days after President Obama's West Point speech announcing his decision to send 30,000 additional troops (on top of the 32,000 deployed in 2009) to the war zone and then begin bringing them home in July 2011, Gates went on the Sunday talk shows to say the withdrawal would depend on conditions on the ground. "The President didn't challenge him," Gelb says. "That tells you most of what you need to know about Gates' role and power in the Administration."