FALLUJAH, Iraq — Unlike many Marines in this dangerous city, Staff Sgt. George Scott could have said "no." He could have stayed home in Ohio with his two young sons.

Pentagon rules limit the number of times reservists like Scott can be called to duty involuntarily. But Scott keeps coming back. He's on his third tour now, and said he'd volunteer for a fourth.

"I like to be a Marine, leading Marines, and being around them," said Scott, who in civilian life is a car dealer service manager in Orwell, Ohio.

With the war in Iraq still raging after three years and the full-time military stretched thin, the Pentagon is counting on, and courting, committed volunteers like Scott to fill the ranks.

Scott served earlier in Iraq with another unit, but volunteered to help the 1st Battalion, 25th Regiment, 4th Marine Division, when it was looking for more troops. Many others also agreed to deploy again: about half of the 500 original members of the 1st Battalion are in Iraq by choice, said Gunnery Sgt. Pete Walz, a spokesman for the reserve battalion stationed in Fort Devens, Mass.

The 1st Battalion's numbers show the increasing reliance on volunteers from the reserves and National Guard, even as the number of reserve units is going down.

CITIZEN WARRIORS

The Iraq conflict, and the Afghanistan fight, have forced U.S. commanders to use reserve forces more heavily than at any other time in recent decades.

During the Vietnam War, active duty troops did most of the fighting. In Iraq, by comparison, the reserve troops made up half of the ground force for much of last year.

After signs that the reserve system was in trouble — including a major recruiting shortfall by the Army National Guard — the Pentagon moved to reduce the numbers of reservists called up. Of the roughly 127,000 U.S. troops in Iraq today, the number of reservists has dropped to about 21 percent, said Lt. Col. Ellen Krenke, a Pentagon spokeswoman.

U.S. commanders have said part-time troops will play a much smaller combat role for the remainder of the war.

Reservists haven't shared only the duty, they've shared the toll. In 2004, about 20 percent of the 845 U.S. military deaths in Iraq came from the reservists' ranks. In the first nine months of 2005 — when an Army National Guard division was sent into battle for the first time since the Korean War — reservists accounted for 36 percent of 595 U.S. deaths.

Though many reservists and National Guard members in Iraq have been assigned to support roles, others have been sent to some of the most violent areas of the country. Scott's battalion is responsible for Fallujah, where militants again are trying to make inroads.

It's no less dangerous for these reservists than for the active-duty Marines.

Last year one battalion of Marine reservists in western Iraq suffered 48 fatalities during a seven-month tour. In the summer of 2005, the Army's Georgia National Guard was stationed in Mahmoudiyah, one of Iraq's most dangerous areas, and quickly suffered several deaths before being moved to a calmer area.

A MISSION THAT MATTERS

Despite the risks and fears of an extended Iraq conflict that have driven many away, others continue to volunteer.

In Fallujah, the Marine reservists who volunteered said they did so for many reasons, ranging from patriotism to a sense of camaraderie with other troops from their hometowns.

"What I tell a lot of people is that we've got to finish what we started," said Staff Sgt. Christopher Hale, of Albany, N.Y., a correctional officer back home who now oversees one of six checkpoints leading into Fallujah. "I knew they needed a staff (noncommissioned officer), and the other guy wasn't going."

Some Marines, particularly those with wives and children, acknowledged the stress of being away for months. Sgt. Mark Sabourin, a carpenter in Bellingham, Mass., said he had a child back home who was "attached to his hip" but yet he still agreed to deploy to Iraq for the second time.

"My biggest reason was to take care of my Marines," said Sabourin, 37, noting that his battalion had several young Marines with only two years of experience. "I wouldn't feel right sitting at home watching these guys on TV, doing what they need to do. That's not why I joined the Marine Corps."

Sgt. Recordo Demetrius, a mechanic taking a break from repairing a Humvee damaged by a roadside bomb, said his wife was a "little reluctant" about his second tour in Iraq. He acknowledged the stress of deployments often falls on relatives at home.

"I think it's harder for the families back home than the Marines who are doing it. Some of them understand. Others are like, 'Why are you doing it?' " said Demetrius, a New York City police officer.

While sometimes their families lack confidence in the mission, many of these Marines said they see important gains in Iraq.

"Every day I think about going home. But if I had the opportunity, I wouldn't. I'd stay here," said Sgt. Manuel Felicio, 31, of Rhode Island, on his first tour.

Scott, too, says he thinks about home and looks forward to spending time with his sons, ages 6 and 10. "It's wearing a little bit," he said, "since my boys are at the age where I should be teaching them to throw a football, how to fish."