Fort Polk, La. ? In training exercises in a mock Afghan village constructed here on a base amid swampland, the U.S. Army is applying the military lesson of the war against the Islamic State in Syria and Iraq: Help your partners beat the enemy, but don’t try to do the fighting yourself.

Letting others fight the battle hasn’t been the American way in modern times, to our immense national frustration. The U.S. military became bogged down in Iraq and Afghanistan, much as it had a generation earlier in Vietnam, by trying to reshape societies with American firepower. For the military, the lesson from these quagmires is to step back — and help local forces with training, advice and airpower.

Fort Polk is a final warmup for the 1st Security Forces Assistance Brigade, one of the Trump administration’s most innovative military experiments. About 1,000 soldiers are being trained here this month before deploying this spring to Afghanistan. The preparatory exercises all focus on the same basic theme: Step back, and insist that partners do the front-line combat.

Gen. Joseph Votel, the Centcom commander who oversees U.S. military operations from Libya to Afghanistan, brought me along on a visit Thursday to the SFAB final training site. He summed up the concept behind the new brigade this way: “We have to let our partners own it. That’s hard for us to do. It’s in our DNA to dive in. But our job is to help our partners fight, not fight for them.”

The Afghanistan simulations are carefully staged in the military version of a movie set, with a mosque tower, goats meandering in the street, peddlers hawking flowers and posters of President Hamid Karzai on the walls of make-believe Afghan National Army (ANA) headquarters. The idea is to make soldiers “comfortable with the uncomfortable,” says Maj. Gen. Gary Brito, the commander at Fort Polk.

Over 14 days of training, the soldiers practice helping Afghan partners reclaim a police station from the Taliban in the imaginary village of “Marwandi” and arrest a Taliban financier who’s sheltered by the local population. In one exercise, soldiers practice rescuing their comrades who’ve gotten caught in a firefight, applying quick tourniquets to their wounds and dragging them to safety.

At each stop, Votel listens as soldiers repeat the new doctrine: “Put the ANA in the front,” says a sergeant heading for Afghanistan. “We have to remove ourselves so it’s not our fight.” Votel replays that unconventional message to the troops through a long day. “What we’re really going to rely on is your adaptability,” he admonishes one advisory team.

When the brigade moves into Afghanistan in several months, it will have 36 combat advisory teams, with about a dozen members each, partnered with ANA divisions spread across the country. Team members will be able to request supporting fire from planes, drones and advanced artillery. Other teams will assist at headquarters and in logistics operations. They will join more than 10,000 U.S. troops already in Afghanistan.

The new brigade, cobbled together quickly with volunteers from divisions across the Army, is an attempt to deal with three issues vexing the Pentagon after more than 15 years of frustration: What works? How can the successful tactics be sustained? And how can the train-and-assist skills of Special Forces — who have been the star players in Iraq, Afghanistan and Syria — be spread across the Army?

Leading this tactical review was Defense Secretary Jim Mattis, a veteran of Iraq and Afghanistan. Last spring, he began a “failure analysis” of what had and hadn’t worked in the battle zones.

The new brigade illustrates a broader process of shaping military plans for the Middle East that’s finally getting traction in the Trump administration, after a year of discussion and delay. Secretary of State Rex Tillerson outlined the Syria piece of this strategic framework this week at Stanford. He argued that America should keep train-and-assist forces in northeast Syria, to aid stabilization there. Walking away from these conflict areas in the past had been a mistake, Tillerson said, but so is trying to steer local governance through nation-building.

America has been so frustrated with combat in the Middle East that people have barely noticed the victory against the Islamic State, and the partnering tactics that made it possible. U.S. collaboration with Syrian Kurds and Iraqi Shiites has made neighboring states nervous, especially Turkey. But it achieved results.

Since the days of T.E. Lawrence, analysts have argued that the people of the Middle East must fight their own battles. This simple but essential idea finally seems to have become hardwired at the Pentagon.

— David Ignatius is a columnist for Washington Post Writers Group.