The Wall Street Journal Weekend features the heartbreaking tale of Lance Cpl. Williams, a Marine who was only member of his 12-man squad to survive a roadside bombing in Iraq. His condition is something similar to PTSD that doctors describe as "traumatic loss" and "moral injury."

Long story short, veterans such as Lance Cpl. Williams "experience guilt over surviving."

Just before the column moved, platoon commander Lt. Col. Chris Toland—then a captain—leaned down from the command hatch and said he had to change vehicles to supervise the Iraqi troops. He wanted Lance Cpl. Williams, his radio man, at his side.

Lance Cpl. Williams didn't want to leave. But he clambered over groggy Marines and out the rear door. He turned and said, "I'll catch you on the flip side."

At first the Marines drove through the desert to avoid booby-traps on the roads. But the Iraqi trucks kept getting stuck, and the Lima Company commander, Lt. Col. Steve Lawson, ordered everyone onto the road.

They hadn't gone very far when Lance Cpl. Williams heard a tremendous explosion. He looked up at an Iraqi security man whose head was poking through a hatch, and saw an orange fireball reflected in his sunglasses.

The rear ramp dropped open, and Lance Cpl. Williams saw a blackened hull spouting flames 30 feet high. First Squad's vehicle had triggered a buried bomb containing artillery rounds and propane tanks. The explosion killed his 11 squad mates, a translator and two crewmen. The driver, not a member of 1st Squad, survived.

Lt. Col. Toland sent Lance Cpl. Williams to the roof of a nearby house to work the radio. The lance corporal watched 2nd and 3rd Squads pile into the building. It dawned on him: 1st Squad was gone.