YAKIMA, Wash. -- With a deafening bang, the mortar explodes.

It's the kind of sound that stops thought and stuns the senses.

For an officer in the U.S. Army, that's not an option.

Within seconds, the squad leader is scrambling troops to dash back through the woods to their starting point.

On a real battlefield, a few soldiers almost certainly would have been killed or badly wounded while overtaking and searching the machine-gun position. But the evaluator goes easy on them this time, ruling only that one soldier suffered a leg injury from the simulated mortar attack.

One lesson at a time, these ROTC students from Central Washington University are learning to lead in combat.

This forest outside Spokane is their classroom for the weekend, a place where roughly 70 prospective second lieutenants will learn the perils of friendly fire, walk through the dark looking for a navigation point, and deal with civilians on the battlefield.

For the juniors, it's their last chance to sharpen their skills before taking a monthlong summer leadership course at Fort Lewis.

The seniors, who have already had their turn, oversee the training with help from the instructor cadre.

The weekend starts with a helicopter ride from Ellensburg as part of a simulated air assault mission.

For the next 48 hours, cadets scramble up and down hills, fire blank-loaded rifles at snipers, develop attack plans, sleep only when ordered and learn to like military Meals Ready to Eat, with a canteen cup of mostly cooked chicken soup to warm up at night.

The idea is to teach these prospective officers how to lead while pushing them well beyond the boundaries of most college students.

"It's incredible for developing people and making you find out what you are capable of doing, and there are a lot of people in all honesty who can't hack it," says Chris Scrupps, a senior who served as the battalion's cadet commander during spring quarter.

"It really helps weed out the best of the best."

In fact, the Army's Cadet Command earlier this year judged Central's Army ROTC to be the best among more than 270 programs nationwide.

ROTC, which was created in 1916, started at Central in 1981. By this year's graduation, nearly 300 second lieutenants will have earned their commission through the school. ROTC is the largest of three ways to become a military officer. The other routes are military academies, such as West Point, and officer candidate school.

Students join ROTC for a variety of reasons.

For senior Jessica Oaks of Selah, who is serving simultaneously in the National Guard, the military gave her a way to attend medical school. She wants to be a pediatrician, and ROTC will give her small-unit leadership experience that's not available in the Army Medical Corps.

Aaron Blanchard, also a senior from Selah, already had five years as an enlisted Marine, serving in Operation Iraqi Freedom. But ROTC gives him the opportunity to become a helicopter pilot, which requires a college degree and an officer's commission.

Kevin Robillard of Granger already had time in the National Guard when he decided to join ROTC. He wanted to "do something meaningful" with his life.

"I know that sounds corny, but that's honest to God," Robillard says during a break between land navigation courses.

Although ROTC programs at the University of Washington and elsewhere have been the focus of protests, Central students and instructors say they haven't seen that here. Once a week, they wear their uniforms to class.

"I've run into nothing but support. Whether or not they agree with us, they know we are doing a good thing -- something noble," Robillard says.

Their lives are a mix of military education and regular college (although they are regularly warned that conduct matters; a drunken-driving arrest could end their career in less time than it takes to salute).

Four days a week, they have a morning run or other exercise. On Fridays, some students may attend a study hall designed to help them maintain their grades. If they have missed an exercise session during the week, they will get to go on a road march, complete with a loaded backpack weighing 30 to 40 pounds.

"That kind of pain enhances learning sometimes," says Lt. Col. Gregory Solem, commander of the ROTC program and a professor of military science for Central.

Cadets also take classes in military history and leadership on their way to earning a minor in military science. Their majors are mixed, although a fair number take political science.

Some are looking forward to military careers; others plan to get out after their standard contract is up; for active-duty personnel, that means four years of full-time service and four years of availability for mandatory recall.

For most cadets, the ROTC experience starts with freshman orientation: a haircut, uniforms and gear, learning to march, being briefed on what specialized training programs are available to them.

About 15 members of this year's 90-member class are from the Yakima Valley. Most come from Washington; about a dozen are women. Nearly three-quarters of the students have a scholarship.

They will go on to serve in a variety of Army branches, from infantry to aviation to engineering.

The graduating seniors were commissioned during a special ceremony last week -- including carrying on a military tradition of passing a silver dollar to the first person to salute them once they have received the lieutenant's gold bar rank insignia -- but some will be waiting for months before being accepted into their specialized training. That's because the military only has so many officer slots available.

After attending more training, they get their first platoon-level leadership assignments, where they will be responsible for directing 20 to 40 soldiers, with active assistance from a platoon sergeant.

Despite producing roughly 40 percent of Army officers, ROTC has long suffered from a reputation problem among enlisted soldiers. For them, the Army is a regular job they've dedicated years to while their new platoon leader was attending college.

But Solem emphasizes that ROTC has outgrown this dated perception and is now widely seen as producing officers equal to those from West Point, for example.

Solem said instructors demand more from cadets than when he went through the program more than 20 years ago.

"We expect a lot out of our cadets. It's not just going to class," Solem says.

Cadet Oaks agrees.

"I wouldn't say it was easy, because the stress you get put under is a lot more than the average college student," she says, adding: "Overall, it's been a good experience."

The recognition as the nation's top ROTC battalion was unexpected, members say.

"I had no idea we would get that. It was a good surprise, because it means we did better than we think we did," Oaks says.

But there's always something to learn.

Blanchard, 28, had his own moment of humility. After two tours in Iraq, he felt like he knew how to do his job. But during an ambush practice, he was "killed" for searching a dead body the wrong way.

Says Blanchard: "That was kind of the turning point. I don't know everything, and I can learn from these guys."