In every presidential election since 1992, the candidate with the less distinguished military resume has triumphed.
Bill Clinton defeated war heroes George H.W. Bush and Bob Dole; National Guard pilot George W. Bush beat Vietnam veterans Al Gore and John Kerry; and Barack Obama was decisively elected over John McCain, who had displayed extraordinary valor during years of captivity as a Navy pilot in North Vietnam.
In 2012, we won't have the chance to test this trend: For the first time in modern American history, neither major candidate for the presidency has any military experience.
This is a dramatic change. The crucible of combat not only created these United States but has also given us many of our most successful presidents.
Our first president, and still the greatest of all Americans, was a general before he was elected; George Washington's leadership of the Continental Army proved that he could handle the challenges of a newborn nation.
William Henry Harrison's short presidency was based in no small part on his victory over the Shawnee Indians at the Battle of Tippecanoe; with Vice President John Tyler, he won on the slogan "Tippecanoe and Tyler, too."
The presidency of Ulysses S. Grant, though marked by scandal,would never have been but for his steady generalship in America's bloodiest conflict.
Harry Truman came to prominence as the commander of a National Guard artillery battery in the First World War in France; his performance in combat powered his rise to the Oval Office.
Service in World War II gave the nation not just Dwight D. Eisenhower but also John F. Kennedy, whose heroism as a PT boat skipper in the Pacific was a counterpoint to Eisenhower's leadership of a great alliance in Europe.
Lyndon Johnson, Richard Nixon, Gerald Ford, Ronald Reagan and George H.W. Bush all served in uniform during World War II, while Jimmy Carter, too young for that conflict, graduated from the U.S.
Naval Academy and served aboard nuclear submarines during the Cold War.
But today, the connection between service in war and election to the highest office in the land has been severed.
How we got here is difficult to ascertain. The sample size of presidential elections is small, and military service is far from the only factor that voters consider. Yet the 2012 White House hopefuls reflect a broader truth: Even in a country waging what seems to be a forever war, military service is increasingly limited to a small swath of volunteers, widely admired but little known.
Early in our nation's history, Americans fought to claim a continent both from its native inhabitants and from foreign powers that coveted its riches. Fighting for the country was a regular part of the American experience, and excellence in that service was one way to demonstrate leadership to the nation.
The pool of citizens who were veterans was broadened by the draft during the Civil War and both World Wars, increasing the number of political candidates with military service and the connection voters felt to contenders with whom they had shared the experience of combat.
Almost all served, and everyone respected those who had - and perhaps even looked down a bit on those who had not been a part of America's battles.
That relationship broke down during the Vietnam War, when not all segments of society were called upon to fight. When Johnson chose not to mobilize the National Guard for combat duty, it became a refuge for the sons of the elite who were avoiding war.
James Fallows has written, movingly and guiltily, of how the most privileged Americans found ways to avoid the draft, sending the less fortunate to war in their place.
The long conflict in Southeast Asia tore the United States in two, destroying an effective consensus about the use of American power abroad. The soldier became the symbol of an unpopular war.
Presidential candidates who had answered the nation's call struggled to connect with voters who often hated the war that had helped form them.
Gore played down his service in Vietnam during his bid for the White House, while Kerry's service became a liability; although he was one of a few candidates to have been wounded in combat, he was "swift boated" by opponents who questioned some details of his service.
No American veteran of any earlier war, let alone another recipient of several Purple Heart medals, would have been treated this way.
But this black mark on America's treatment of its veterans is fading. In the wake of Vietnam, the country chose to meet its national security needs with a force composed entirely of professionals who had volunteered for duty.
This force has proved enormously capable - triumphing in Desert Storm, easily defeating both the Taliban rulers and Saddam Hussein's army, and demonstrating adaptability when performing counterinsurgency in Iraq and Afghanistan.
No one who has served in today's military would countenance a return to the draft and a force composed at least in part of Americans compelled to serve. The small size of the military relative to the population - well under 1 percent - makes broadening the service base both unnecessary and unlikely.
But there are costs to this all-volunteer military that are not immediately apparent, even on this weekend dedicated to remembering its sacrifices. The disconnect between those who give the orders and those who have no choice but to follow them has never been wider; all Americans salute the same flag, but only a few carry it forward against enemy fire.
The military has become a caste apart from the nation it protects, with many of its fighters the sons and daughters of military leaders - a family business that asks much of a few.
Service academy alumni journals are full of photos of multi-generational family reunions in combat zones, while most of us do no more to support the troops than stand, remove our caps and cheer when they present the national colors before a baseball game.
Now, nearly 30 years into this experiment with an all-volunteer force, and more than a decade into America's longest war, the nation will elect a president who has not known the tender courtesies of a drill sergeant at oh-dark-thirty in the morning.
Military service is not the only way to demonstrate dedication to country or capability for high office, of course; Franklin Delano Roosevelt was one of our greatest presidents despite never wearing a uniform, although his appointment as assistant secretary of the Navy gave him a useful perspective on the military he would lead with such distinction.
Both President Obama and Mitt Romney have demonstrated impressive leadership in government, education and business. Obama's bona fides as commander in chief are clear; he has shown his resolve in the pursuit of Osama bin Laden and the effective dismantling of al-Qaida during his administration. The first lady's dedication to military families, worn down after years of war, is exemplary.
Still, the choice to take the nation to war is the most important decision a president can make. A commander in chief who has actually served on the battlefield has peerless personal experience and can make that decision with greater empathy.
And after this election, there will be a new generation waiting to enter the political arena, veterans of a tough decade of war in Iraq and Afghanistan.
Unlike those who fought in Vietnam, the veterans of these wars have been embraced by an American public that supports the troops, even if they oppose the conflicts in which they fought. The admiration offered to today's veterans bodes well for the prospects of future political candidates who have known firsthand the burden of carrying out the orders of the president abroad.
Wars have given the United States many of its most important political leaders, and we can expect those who have led this country's sons and daughters in the sands of Anbar province and the mountains of the Hindu Kush to turn their sights to the highest office in the land in years to come.
When they do, these veterans will lead the nation back to its foundations. Forged in war, they will work to build a better peace.
John Nagl, a retired Army officer, is the Minerva research fellow at the U.S. Naval Academy and a veteran of both wars in Iraq. He is the author of "Learning to Eat Soup With a Knife: Counterinsurgency Lessons From Malaya and Vietnam."
The Opinion section is produced by the Editorial Department to foster discussion about key issues. The Editorial Board represents the institutional voice of the Star Tribune and operates independently of the newsroom.