SAN DIEGO — Perched atop a stack of foot lockers in a spotless barracks, drill instructor Gunnery Sgt. Celestino Casias asks 45 shaven-headed recruits what it takes to be a Marine. "Honor, courage, commitment!" the aspiring fighters shout in unison.

The words come easy in this new class about ethics, but allegations that Marines killed women, children and unarmed captives in Iraq and Afghanistan suggest they may sometimes prove hard to live by.

"When you are out there, you are going to be challenged ... and it's not just in Iraq or Afghanistan," said Lt. Col. Robert Scott, commander of a recruit battalion at Marine Corps Recruit Depot in San Diego.

"When you are on the horns of a moral dilemma, you need to refer back and think, 'What would my senior (drill instructor) do?' "

To give recruits answers to that question, the Marine Corps is boosting training in values and battlefield ethics, requiring more hours of lessons on the issues than any other branch of the military does.

The Marine Corps commandant, Gen. James T. Conway, ordered the initiative in November, and a more rigorous diet of ethics training was introduced in May at the San Diego recruiting depot — one of the service's two training centers for enlistees, graduating about 20,000 Marines a year.

"No one is prematurely judging guilt or innocence," Conway said in a speech Tuesday in San Francisco. "But the very convergence of all these events concern me and so we're examining as a Corps how we prepare our young squad leaders."

Conway routinely tours Marine bases and shares with the troops his concerns about the pending criminal cases, said a spokesman, Lt. Col. T.V. Johnson.

"He wants to make sure we are making Marines the way we used to," Johnson said. "If you look at the respect the American public has for Marines, each one of these incidents is a withdrawal from the bank of respect."

The most notorious active case is the 2005 killings of 24 Iraqi civilians at Haditha. A Marine squad used grenades and gunfire on the Iraqis after a roadside bomb killed a Marine. Women and children were among the dead.

Three enlisted Marines are charged with murder and four officers are accused of failing to investigate the deaths. The defendants say they killed the Iraqis because they believed they were under attack.

A Pentagon survey of 447 Marines in Iraq last year found fewer than half said they would report a member of their unit for killing or wounding an innocent civilian. Only 38 percent said noncombatants should be treated with dignity and respect.

During 12 weeks of boot camp, Marine trainees get 38 hours of values training, up from 24. The Army provides about 24 hours of instruction on core values and ethics, the Air Force 7 1/2 hours and the Navy about five hours.

"It's about having the moral courage to do the right thing all the time," said one of the drill instructors, Sgt. Michael Dequatrro, 26.

The lessons start off simply: don't drink and drive, never sleep on guard duty, don't fraternize with officers.

Then tougher issues are introduced, including what it means to kill someone.

"At the beginning, we are like puppies being trained up," recruit Juan Baldelomar, 23, said a few days before he graduated. "Now, we are more accountable."