Out in the burning California desert, the Army is trying to figure out how it will win America's next war.

As the post-9/11 counterinsurgencies in Iraq and Afghanistan cool from a boil to a simmer, the Army's National Training Center at Ft. Irwin remains America's premier high-tech war game battleground. The Army spares no expense training each brigade undergoing a three-week NTC rotation, spending millions on the evaluators, fuel and ammo required.

The big question is what they're training for -- and part of the answer lies in whom they are training.

In the '80s and '90s, the NTC focused on how to beat the Soviets, America's most recent true "peer threat." NTC even had its own Soviet-style force, the "OPFOR" from the nation of "Krasnovia" that knew the hills and wadis of NTC's battlefields as well as it knew Soviet tactics. The massive force-on-force battles -- using lasers to record hits on people and vehicles -- were taped and ruthlessly analyzed. The consensus of the Desert Storm vets who eviscerated Saddam's Republican Guard in 100 hours was that the war had been won at NTC.

Today, Krasnovia, like the USSR, is no more. It has been replaced by "Atropia," a beleaguered U.S. ally suffering both the same counterinsurgency problems as America's real allies, plus a looming enemy conventional army. In other words, the new threat is everything -- from bands of insurgents planting IEDs up to armored formations of T-90 tanks.

The doctrine addressing this hybrid threat has a name -- "Decisive Action." But the strategic problem it poses does not yet have a clear answer.

Complicating matters, the defense budget is in freefall, and the number of brigades is set to drop. The Army faces this uncertain future, potentially fielding a smaller force than it has since before World War II -- and, critically, one in which no one with less than a decade of service has trained to fight an enemy that can stand toe to toe with U.S. forces.

The new Army must adapt to these realities, and one of the biggest changes is already well in process -- namely, a dramatic increase in the Army's reliance on the battle-proven forces of the reserve component. The first light infantry brigade combat team to go through an NTC Decisive Action rotation was not an active duty unit from the 82nd or 101st, but a National Guard brigade. The Army will never go to war again without its reservists.

The "weekend warrior" stereotype of reservists is long gone. Almost all of those citizen-soldiers have one or more combat zone deployments. They tend to be older than their active counterparts, and thus their units bring to the table more civilian skills -- useful because Decisive Action requires dealing with indigenous people and officials. Because they tend to have more stability in units, the reserves are also a vast reservoir of soldiers with greater collective memory of training against the Soviet hordes.

Reservists also share the toughness and humor that has always distinguished American warriors. During the rotation, a Guard soldier had a .50 caliber blank round accidentally detonate in her hand, blowing off most of her thumb. After treatment, she asked to return to her platoon, arguing, "It wasn't my trigger finger!"

While the Army cannot know exactly what the next war will be, it has a pretty good idea of who it will need to fight it.

Col. Kurt Schlichter is the deputy commander, 79th Infantry Brigade Combat Team, California Army National Guard. The views he expresses are his own.