Among his fellow generals, Gen. Martin Dempsey is well respected and known as an extrovert, prone to belting out Frank Sinatra standards at formal Army social events.

He was sworn in as Army chief of staff only last month, but will give up that position in the fall to replace the retiring Joint Chiefs of Staff chairman, Adm. Mike Mullen. He has spent much of the past decade leading troops in a messy, low-tech war in Iraq and is deeply skeptical of technology's ability to alter the basic nature of combat.

"We operate where our enemies, indigenous populations, culture, politics, and religion intersect and where the fog and friction of war persists," he wrote in the introduction to the Army's main operating concept.

Like many senior Army officers, Dempsey's view of combat has been shaped indelibly by his searing experience in Iraq. In May 2003, he assumed command of the Army's 1st Armored Division, which was struggling to put down a growing anti-U.S. insurgency that was taking root in Baghdad. As the commander of 20,000 soldiers in Baghdad, he oversaw a series of major operations designed to weaken the insurgency. Some of the big offensives knocked the fledgling insurgency back on its heels, said retired Col. Peter Mansoor, who commanded under Dempsey.

In spring 2004, militia fighters loyal to radical Shiite cleric Muqtada al-Sadr launched a major uprising. Dempsey flew to Kuwait, where his troops were preparing to board planes home, to tell them personally that the Pentagon had extended their tour for 90 days. His forces put down the uprisings, then started a major effort to persuade the militia fighters to lay down their arms and take jobs cleaning up the battle damage.

Critics say Dempsey has not pushed the Army to think hard enough about future wars. But he emphasized that even the most sophisticated technology couldn't erase uncertainty on the battlefield or substitute for the judgment of a soldier on the ground, a lesson learned through painful experience in Iraq and Afghanistan. Said one officer: "His message was that we can't put ourself in a hole now because we are so worried about what is going to happen 25 years from now."