He looks like a wiry, weather-beaten cowboy, a coiled spring with a leather face. He talks quietly, in measured phrases. With a neutral accent you can’t quite place, his speech has a comforting cadence. Still, you can almost feel the dynamic tension in his brain as he pauses from time to time to choose his words carefully.

He is U.S. Army Gen. David Petraeus, the boss of Central Command. He is responsible for everything that happens—or fails to happen—in an area of operations that spans 20 countries in Southwest and Central Asia, including two where American troops face danger and death every day: Iraq and Afghanistan.

As President Barack Obama recently studied his national-security team’s recommendations on how to prosecute the war in Afghanistan, I spoke with Petraeus at his headquarters at MacDill Air Force Base in Tampa, Fla.

Thirty-five years ago, I was an Army captain on the faculty at West Point, and Petraeus was a young cadet there. I remember him well. He was soft-spoken, but his eyes betrayed an intense, almost burning, spirit. I asked him why he became a soldier in the first place, and he said, “I lived not far from West Point and became familiar with its people. They had discipline and were dedicated, and I wanted to be just like them.”

Petraeus graduated among the top 5% of his class and chose to join the infantry. He became a paratrooper and a Ranger and was promoted rapidly. The Army sent him to graduate school, and he earned a Ph.D. from Princeton. In 2000, he was promoted to brigadier general. His subsequent rise from one star to four was extraordinarily swift.

Some critics say that Petraeus has always been voraciously ambitious, with his sights set on the highest rank and responsibility, but the general himself said, surprisingly, “Even at West Point I was never committed to a long career in the Army and instead fell in love with it incrementally.” Whatever his thirst for authority, he is now in charge of campaigns whose outcomes will affect America’s security for decades to come.