The highly emotional debate over whether women should be allowed in combat positions in the U.S. military is back. The latest firefight was prompted when the only female officer enrolled in the Marine Corps’ Infantry Officer Course dropped out after failing to complete two conditioning hikes, according to Corps’ Training and Education Command. As a result, “There are no female officers enrolled or slated to attend” the course.

Now Donald Trump has weighed in, declaring that women should be put in combat slots “because they’re really into it. And some of them are really, really good at it.” Um, like whom? Demi Moore as a Navy SEAL in GI Jane? (A movie I disliked because as hard as it would be for a woman to become a SEAL, it’s impossible to be a GI—which means Army—while in the Navy.) Hillary Clinton, of course, also supports it, because she’s a “huge supporter of women being able to break whatever glass ceilings are holding them back.”

But this is an issue where neither politics nor ideology has any place—because it’s a matter of life and death. The purpose of the military should be to accomplish violent overseas missions with minimal casualties. The military is not a democracy, and its purpose isn’t to provide equal opportunity. It is highly discriminatory, based not on skin color or religion but ability.

There should be data on whether women perform as well as men, and that should be the determinant. And indeed there are, including data on a huge factor that few people bother to consider because they lack the experience of those who have used it, as I have: body armor.

body armor front
Body armor saves lives. But it’s not fun to wear. Trust me. The newest weighs about 3035 pounds depending on the size of the wearer, and the helmet adds another 34 pounds. Counting all equipment, the Marine Corps puts the average combat load at 83 pounds. And unlike your cotton shirts, ceramic plates don’t ventilate. For these reasons, while I seemed impervious to bullets and bombs, armor almost killed me on one trip overseas as a paratrooper-turned-photojournalist. Damage from another combat trip has probably left me permanently crippled.

On the first, outside Fallujah, the heat, in addition to other factors such as lack of sleep and a prior medical condition, caused my colon to explode—ironically, as I was blowing up IEDs with an Explosives Ordnance Disposal team. This led to an emergency bowel resection to save my life, plus six subsequent surgeries. On my last combat mission, in the mountains of Afghanistan, the armor plus extra gear that I carried for my job herniated two disks, which led to a bout of horrific sciatica right when I came home and more recently a second one that will probably leave one foot permanently twisted and weakened. Yet I was in excellent overall shape prior to both incidents and am quite strong even for a male.

But females?

A 1992 Presidential Commission report found that “The average female Army recruit is 4.8 inches shorter, 31.7 pounds lighter, has 37.4 fewer pounds of muscle, and 5.7 more pounds of fat than the average male recruit. She has only 55 percent of the upper-body strength and 72 percent of the lower-body strength.” Further, “The average 20-to-30 year-old woman has the same aerobic capacity as a 50 year-old man.” In the mountains of Afghanistan, many miles above sea level and with air thinner than blouses at the Oscars, running even without body armor can feel like breathing from the tailpipe of a Bangkok bus.

According to the Surgeon General’s office in 2011, “Army women are more likely to be disabled than men and are approximately 67 percent more likely than Army men to receive a physical disability discharge for a musculoskeletal disorder.” They’re more than five times as likely to suffer stress fractures. Snap, crackle, pop.

Countless other studies have produced similar results, but you could see them just by turning on your TV this past month. Look at winning Olympic scores for any sport involving strength. There’s a reason why the Olympics segregates male and female athletes, and it ain’t sharia law.

Not surprisingly, a Marine Corps evaluation last year showed that all-male units greatly outperformed mixed-gender units in just about every capacity. The women performed their tasks more slowly, fired weapons with less accuracy, and sustained far more injuries during training than their male counterparts. Male Marines with no formal infantry training outperformed infantry-trained women on each weapons system. And much of that is body-armor-related. When you’re exhausted, you fire less accurately, make more mistakes, have more accidents, and even have lower morale.

But what if a few women are able to perform as well as men? Or even just one? Can’t we let those few into combat slots? That’s where physiology goes out the window and politics enters. Under pressure from above, bars will be lowered. I saw that a quarter-century ago in Airborne School, where the women did a fraction of the training we men did. Yet the Silver Wings they were awarded didn’t have an asterisk appended.

None of this is to slight the value of women to the services. The most important muscle is the brain: women don’t lack there. And courage? My own public-affairs “handler” in Ramadi, USMC Major Megan McClung, was blown up by an IED during a non-combat mission she presumably volunteered for. (Rest in peace, Megan.) Women are absolutely vital to every branch of the U.S. military. Likewise in most other countries.

Yet virtually no countries place women in combat positions. What you’ve heard about Israel is a myth; as in Russia during WWII, Israel has put women into combat only during dire emergencies. With the U.S. military steadily shrinking (40,000 fewer soldiers by next year), there’s hardly a shortage of men for combat slots. Putting females into those positions may give some a warm and fuzzy feeling, but it’s a recipe for mission failure and the needless deaths of good men and women. And that’s far too high a price to pay to make anyone feel good.

Michael Fumento, U.S. Army Airborne 1978–82, is a journalist specializing in science and health issues, an author of five books, and an attorney. He was embedded three times in Iraq and once in Afghanistan. He can reached at fumento[at]gmail.com.