"Send in the Marines" has been uttered by every president since Thomas Jefferson sent a detachment of leathernecks to the shores of Tripoli in 1801. These words are likely to be uttered in the next four years — which is of special interest to me as a Marine who has served multiple combat tours in Afghanistan and Iraq.

Veteran status is no guarantor of a leader's successful use of the military, of course; nor is its absence necessarily a harbinger of misuse. But in the 1970s, 74 percent of Congress had prior military service. Today: 23 percent. Barack Obama, though respectful of the military, has no service record and only two veterans in his Cabinet — the fewest since Herbert Hoover. By contrast, John Kennedy, decorated for heroism in World War II, had only two Cabinet members who weren't veterans.

These figures reflect a disturbing trend, with the military and civilian worlds warily eyeing each other across a cultural no man's land. As tightening budgets shrink future forces, veterans will be fewer and the chasm wider — to our peril.

No one wants everyone to think and act alike — diversity is a major source of our nation's strength. But this diminishing shared experience leaves us ill-prepared to defend against global terrorism. As Gen. William Butler warned a century ago, "A nation that insists on a broad line of demarcation between the fighting man and the thinking man is liable to find its fighting done by fools and its thinking done by cowards."

The demographics of today's military — strained as we are — offer hope. In 2007, 99 percent of recruits were high school graduates (vs. 84 percent nationally), and 95 percent of officers had bachelor's degrees (vs. 27 percent nationally). Exploding the myth that enlistees have no other options, 50 percent of recruits came from the wealthiest two-fifths of neighborhoods, but only 29 percent from the poorest two-fifths. We also mirror the country's rich diversity: 34.5 percent of recruits belong to a racial or ethnic minority (vs. 34.2 percent nationally).

The physical excitement of combat isn't the attraction. It's the opportunity to make a difference. We don't leave our families for the paycheck, we don't deploy into a combat zone for the living conditions and we don't ensure that there is a round in the chamber because we want to shoot someone. Our motives, like war itself, are complex, layered and visceral.

During the darkest days of World War II, George Orwell allowed that "we sleep safe in our beds because rough men stand ready in the night to do violence to those who would harm us." That is what we do — but only when we do it right. Service members, like cops, have clearly defined codes of conduct, the strength of which leads to outrage when they are violated, whether by a cop abusing suspects or a soldier abusing prisoners. The outrage is particularly acute among those who share the code: No one hates a bad cop more than a good one.

But if we limit the honor and physical courage of the warrior ideal to an isolated subculture of military, police and firefighters, focusing them solely on those virtues, we risk cultivating doers less tolerant of different lifestyles or ways of thinking. And if we limit aesthetic appreciation to the world of academics and economic elites, never encouraging them to roll up their own sleeves, we risk fostering gifted thinkers great on nuance, but subject to paralysis by analysis.

Or worse. This artificial separation forces us to confront global terrorism with either the compassionate consensus of the whole-foods collective or the indiscriminate anger of the lynch mob — failures both.

Without greater understanding between the military and civilian worlds or, better, a return to a synthesis of the two, we risk a future without all of us working toward the same ends — whatever society decides those ends should be. And we risk misusing military force because of misunderstandings about what it can and can't do or, once used, its being prematurely withdrawn because of unrealistic expectations. The solution is an educated citizenry that understands its soldiers, sailors, airmen and Marines — understands that we are you.

Matthew Bogdanos, author of "Thieves of Baghdad," is a colonel in the U.S. Marine Corps Reserves. He wrote this article for The Washington Post.