When, recently, I asked a helicopter pilot friend of mine what he thought about Brian Williams, the venerable NBC nightly news anchor, suspended after an apparent lie about his helicopter being forced down by a rocket-propelled grenade in Iraq, he couldn't believe it.

“Why would you freaking lie about something like that?” the pilot asked.

He liked Brian Williams, even nodded off to sleep on his last deployment to Afghanistan while listening to the NBC nightly news podcast. I was more cynical. In 2003, who wasn’t lying about the war, and why wouldn’t you? There were no real consequences for the liars—then or now—and so I kept thinking about it.

There is one R.P.G. story I know that is incredible and all true. I first heard about it as a soldier in Afghanistan in 2006, when this happened to another company in my battalion. There’s some lying in this tale. Not all soldiers are saints. But the lying here is done to save a life, rather than aggrandize or pad a life story. It’s been reported before, but I thought it worth revisiting in the weeks after the Williams scandal.

On March 16, 2006, five years after the invasion of Afghanistan and three years after the invasion of Iraq, a platoon from Alpha Company, 2-87 Infantry set out from Forward Operating Base Tillman in eastern Afghanistan. About an hour into the patrol, the five armored Humvees and a soft-skin Afghan National Army pickup truck stuffed with about 10 local soldiers that composed it took fire. There was lots of shooting from both small-arms fire and R.P.G.s. One Afghan soldier died almost immediately when the pickup truck exploded.

An R.P.G. is a simple weapon—a launcher and a rocket with a shaped charge of explosives. At 1,300 feet, it can punch a hole two inches in diameter through more than 11 inches of armor, according to the official assessment of the R.P.G.-7 by the U.S. Army. Designed as an anti-armor weapon for infantry use in the event of World War III, it has become the warzone equivalent of a prescription drug with multiple off-label possibilities. As such, it’s been a reliable battlefield presence in almost every war and conflict since World War II.

On March 16, 2006, attackers fired on the Alpha Company platoon from a ridgeline 300 meters away. One such R.P.G. first hit a Humvee, turning shards of the vehicle’s protective armor into sharp shrapnel. As I revisited the story last week, I spoke to Staff Sergeant Eric Wynn, who himself suffered devastating injuries in the attack when an R.P.G. sliced past his face.

“My nose was sheared off,” Wynn told me. “When I opened up my eyes I could feel blood pouring down my lips. I turned to Moss to get him to return fire. That’s when I noticed the R.P.G.’s tail sticking out of Moss.”

Flying further, the R.P.G. had come to rest sticking out of the abdomen of Private Channing Moss, a 23-year-old turret gunner from Georgia. Despite his own injury, Wynn had the presence of mind to call the patrol’s commander, Lieutenant Billy Mariani.

This was extraordinarily bad. Moss was still alive, but he appeared to have an unexploded grenade inside him, with enough power to kill everybody inside the Humvee, should it explode. Its tail, sticking out of a smoking wound, left no indication of how much explosive—if any— was left in the warhead or in its detonator. The round could have been a dud, or a warhead that failed to arm but that still could explode. Unexploded ordnance in Afghanistan, especially old Soviet technology or Chinese knockoffs, wasn’t known for its stability.