Any culture that pushes its women toward the battlefield is a culture plunging toward destruction. Only a degenerate culture substitutes women for men in war. It doesn’t deserve to survive and, in the very long run, probably won’t.

In a parting act of vandalism, President Obama has expressed his support for requiring 18-year-old women to register for the draft.

But it would be unfair to blame only Obama. Nominal “conservatives” and military brass have joined the conga line. And taking sophistry to a new level, even libertarians repulsed by the very idea of conscription are supporting the initiative on the principle that what’s good for the gander is good for the goose.

Have you people lost your minds?

I’m not a fanatic, and I respect and admire women who wear the uniform. From 2007 through 2009, I was a civilian contractor for the U.S. Army in Iraq, and some of the best young intelligence officers there were women. But men and women are not interchangeable, and the attempt to make them so is destructive socially and ruinous militarily.

I view this issue as an anthropologist, a student of history, a Vietnam veteran, and a former journalist who has done some reporting on the military. Until very recently, every known society has had a taboo against sending women to fight while healthy young men were still available. Taboos, such as the incest taboo, develop when the rewards of an activity are immediate and obvious but the penalties are shrouded and delayed.

In the current all-recruited force, the short-term benefit of relying on 42-year-old grandmothers and lactating mothers is clear: it makes up for the male no-shows. As the late Charles Moskos, the dean of U.S. military sociologists, put it: “Americans seem to prefer somebody else’s daughter dying rather than their own sons.” So wouldn’t drafting women be a salubrious corrective? No. Instead it would be a step toward enshrining the interchangeability falsehood. We don’t need to draft women. Since the end of the Korean War, we’ve had more young men of military age in the U.S. population than the armed forces could possibly absorb.

We’ve been able to get away with this debased method of staffing our military because the United States still is a vast, rich country that—although it engages in distant, elective, brushfire wars—still holds a huge advantage in resources, population, and technology over any probable combination of existential enemies. I define an “existential enemy” as a coalition that could defeat our main forces, occupy our homeland, or hammer the United States back into the status of a regional power.

The long-term costs of violating the taboo are hidden but deadly. Our survival as a society is geared not to good conditions, or even average conditions, but to an ability to get through the worst crises. Militarily, that worst crisis is total war, but even in World War I and World War II America got off easy in terms of manpower. (Only the Confederacy approached full mobilization.) With the exception of the Soviet Union, which ran out of men during World War II, none of the major 20th century belligerents pushed women toward combat.

Why? Because men fight better than women, and men fight better when women aren’t around.

War is the great auditor of institutions. All other things being equal, an army of men will beat an army of women. All other things being equal, a society that puts women in the field at the expense of fielding a like number of men will lose its wars. Luckily, all other things aren’t equal, which is why we’re still here.

On December 3, 2015, Secretary of Defense Ashton Carter announced that all military roles would be opened to women, including those in first-line ground combat units whose mission is to locate, close with, and destroy the enemy. In preceding decades, the public had come to accept the presence of women in support units. But even this is misguided for three reasons.

First, support troopers in combat zones are required to perform heavy physical labor more suited to men than women. This includes such tasks as digging entrenchments, filling and stacking sandbags, and moving ammunition crates. The more fluid and chaotic the battlefield, the more these things must be done by hand rather than by machine.

Second, to use a sports metaphor, support units are the infantry’s “bench,” or reserve, and if it’s necessary to use the “bench,” the situation is out of control by definition. It’s not something your own leadership decides. It’s a condition the enemy imposes. The worse the situation on the ground, the more blurred becomes the line between the infantry and everyone else. And when women dilute the pool of reserve infantry, the commander has less force and fewer options at his disposal.

In 1942, for example, PT boat sailors, fighter pilots, and ground crews were assigned infantry duties on Bataan. Late in 1944, the German counteroffensive in the Ardennes was stopped largely by the work of small, isolated combat engineer units (now sexually integrated) fighting as infantry. After the Luftwaffe was all but destroyed, U.S airmen were ordered to Eisenhower’s depleted infantry divisions as replacements—even though the Allies had the initiative at the theater level.

In the summer of 1950, in Korea, the 34th Regiment of the Army’s 24th Infantry Division was almost wiped out and had to be reconstituted from support troops. The backbone of the new regiment was the 3rd Engineer Battalion, but soldiers also were taken from supply, ordnance, communications, and headquarters assignments to fight as riflemen along the Naktong River at the Pusan Perimeter. And, of course, during the withdrawal from the Chosin Reservoir the following winter, Army and Marine support troops had to fight as infantrymen.

No good would have come from women being involved in these operations at the expense of a like number of men. The deeper the “bench,” the stronger the army.

The third reason why women don’t belong in support units is the matter of sexual attraction and distraction, favoritism or even the appearance of favoritism, as well as damage to unit cohesion and morale. In Vietnam, I commanded a company in a support battalion that then was all male but now is mixed sex. I shudder to think of how much more difficult my job would have been if the outfit had included women. The military isn’t just another “job,” and you can’t go home at the end of the day.

In 1988, as a reporter, I covered the deployment of U.S. forces to the mountains of Honduras. While frustration, heartbreak, and jealousy didn’t seem to be a problem for the Army reservists and National Guard members who came into the camp and returned to the United States after a few weeks, they certainly were present among the sexually mixed camp cadre, who had to live with each other for almost a year.

How about Iraq? Let’s just say that, on missions, the chatter over the Humvee intercoms was both enlightening and consistent with my earlier observations. Human nature doesn’t change, and we are asking for trouble by pretending it has or will.

As for pregnancies, some instances are intentional as a form of malingering and a way to shirk overseas assignment. Women also have a much higher injury rate. And there is the matter of children left motherless by repeated deployments.

It was drilled into my head when I was on active duty that the mission came first and the welfare of the people I led came second. Aren’t those who demand equal opportunity for women in combat violating that most basic principle of military leadership? What’s good for individual careers isn’t necessarily good for the country.

The mission of the armed forces is to win wars, not under the best conditions or average conditions but with a margin for error under worse conditions than can be imagined. In extremis, the country that puts women in the field at the expense of men will lose. Meeting such a crisis successfully is never easy, and it might become impossible if our culture changes to the point where American men are no longer embarrassed to have women do their fighting for them.

This essay incorporates material the author has published in other forums.