A humvee at the U.S Military Academy in West Point, N.Y. on Sept. 8, 2016. (Jabin Botsford/The Washington Post)

Michael H.C. McDowell is a recent member of the advisory board of the Citadel, the military college of South Carolina.

On May 9, my wife and I lost our only child, H. Conor McDowell — just turned 24, a newly promoted Marine first lieutenant, days away from being engaged to marry his girlfriend, Kathleen Bourque.

He was killed instantly when his light armored vehicle (LAV) turned belly up, crushing him, as he led a patrol in challenging terrain at Camp Pendleton in San Diego County. Conor pushed his gunner to safety but did not have time to save himself.

Conor is just one of too many young people who are dying, needlessly, in so-called training accidents in our military. Over the past year, nearly four times the number of troops have been killed in training rather than in combat.

Vehicle rollovers seem particularly avoidable. Examples we have found, dating just from mid-April:

Joshua Braica, 29, a Marine staff sergeant, father of a 7-month-old boy, died April 14, less than 24 hours after his dune-buggy-like, doorless MRZR vehicle tipped over at Pendleton, crushing his spine. Our son died May 9. Jacob Hess , 34, an Army staff sergeant, died at Fort Polk, La., in a Humvee rollover on May 15. Christopher Morgan , 22, a rising senior at the U.S. Military Academy, died June 6 in another rollover, this time in a five-ton truck transporting two dozen cadets to a training area. Hans Sandoval-Pereyra, 21, a Marine lance corporal who came to the United States from Bolivia during elementary school , was killed when his Humvee rolled over as he trained in Northern Australia in May. In Alaska on June 14, paratrooper Marquise Elliott , 25 and recently engaged to be married, was killed when his Humvee flipped onto its side.

That’s six rollover deaths in 62 days.

Why do these “accidents” continue to happen?

Here’s some background: The vehicles, or “vics,” come back from Iraq and Afghanistan worn out; they are retrofitted or sometimes cannibalized to repair other vehicles, and they often break down. Troops in training can find themselves on difficult territory in potentially unreliable machines.

Range safety officers usually monitor training paths in advance. Is this being done regularly, and if so, how come the 18-foot hole, apparently concealed by tall grasses and weeds at Pendleton, was unknown to our son before his LAV hit the deep ditch and overturned?

How lengthy and how rigorous is current training for drivers? Or for gunners and other specialists? Are we putting our young men and women into these tough positions too soon, and thus endangering their comrades?

What is an acceptable risk in training? Is a 4-to-1 ratio in training to combat deaths acceptable? Is that a wise spending of “blood and treasure,” to use a brutal cliche?

And if it is not wise, not acceptable, is it not wrong to call these tragedies “accidents”?

Here is a key passage from our son Conor’s handwritten journal, dated Sunday, Dec. 2, 2018, during a training operation at Fort Irwin, Calif.:

“Blue 1 Platoon had a rollover. No injuries. LAV dropped 8 feet onto turret, then onto side. 2 medical vics, 6 recovery vics going to site of rollover. Marines will be assessed and cared for. LAV will be left in place until daylight. Pictures will be taken as there will have to be an investigation. 7 Marines were on board. My job just got a lot more serious. Time to monitor the net for information requests. They’ll need a hoist. This isn’t the end of the world but we got really lucky. No injuries involved. . . . This is the second Charlie Company rollover in two months. One of the Marines was in both rollovers. . . . It’s a miracle no one was killed. Sounds like someone got fired. The tone in Chain of Command has sombered somewhat. This is a reminder that at any moment, through careless action, even in training, Marines can die. . . . all of Charlie Platoon’s commanders have now rolled over a vehicle.”

Five months later, Conor himself would perish in a rollover.

Maryland’s senators, Democrats Ben Cardin and Chris Van Hollen, have written to the Navy secretary asking for a serious investigation into all rollovers. The Marine commanding general of Pendleton is conducting an inquiry. But the military must not be allowed to act as a judge in its own cause.

What is needed, urgently, is for Congress to insist on a truly independent, rigorous Government Accountability Office examination into rollover deaths. Until that is done, Congress must force the military to take temporary measures to lower the rate of fatalities.

The Pentagon will make the tired “comparing apples and oranges” argument — and yes, different vehicles are involved in these tragedies, and yes, they happen on different training grounds. But apples and oranges are . . . fruit. These are our troops. Our military leaders and our elected representatives have a responsibility to protect them now.

Soon, the National Defense Authorization Act will be up for reauthorization; Sen. Cardin has submitted an amendment mandating a serious inquiry, and it is gaining Republican support.

Meanwhile, there will be more accidents. And more young men and women in uniform will almost certainly die.