CHATTAHOOCHEE NATIONAL FOREST, Ga. — Dozens of Ranger School students lined up at the base of a 3,166-foot tall mountain here on Tuesday morning, dread hanging on some of their faces. The soldiers, wearing boots and camouflage uniforms, needed to make a 1.8-mile climb in an hour while carrying rifles and about 45 pounds of equipment, ascending some 1,000 feet through rocky trails and thick tree cover to a clearing above.

“It’s simple, guys: Short walk, big hill,” said Army Capt. Kyle Fitchtner, their company commander. A moment later, he added a sarcastic word of encouragement: “Let’s go, Rangers — America can’t keep itself free, right?”

The climb up Mount Yonah was a routine part of Ranger School, but it also made history. For the first time, it included women who are tackling the famously difficult leadership school’s 20-day Mountain Phase. Three female soldiers advanced to it for the first time last week after completing the first of Ranger School’s three phases of training at Fort Benning, Ga. If any of them advances again, she’ll move on to the Florida Phase, learning swamp and jungle warfare tactics, and potentially become the first woman ever to graduate Ranger School.

The women are attending as part of an ongoing assessment by the military about how it should better integrate women into combat roles in the military. It followed a 2013 decision by top Pentagon leaders to open all jobs in the military to women by 2016. The services were required to conduct research first, and are permitted to request an exception to the new policy in coming months for any jobs they want to keep closed, provided they can show evidence that it wouldn’t work.

Nineteen women started Ranger School on April 20 as part of the first class ever to include female students. If any of the remaining three complete the course, they will be allowed to wear the Army’s Ranger Tab, a prestigious decoration, but will not be allowed to join the elite 75th Ranger Regiment, which performs raids and other Special Operations missions. Many male soldiers, ranging from pilots to artillerymen, also earn the tab and serve in roles outside the Rangers.

The military did not allow any of the three women to speak to the media, but it did permit a small group of reporters to observe the first days of the Mountain Phase.

The effort has faced intense scrutiny inside and outside the military. Some critics have questioned whether the remaining women have been afforded unfair opportunities, while others say the majority of the women already have washed out because the Ranger instructors grading them faced pressure to do so.

Col. David Fivecoat, commander of the Airborne and Ranger Training Brigade leading the assessment, said it’s inevitable that “you’re going to get hammered from both sides.” He’s instructed his staff to continue doing their job as it always has, he said.

“We’re a learning organization, and this is the first time we’ve done it,” he said of the gender assessment. “We’re trying to make sure everyone has a fair and equal chance to the earn the tab.”

Eight of the initial 19 women made it through the initial Ranger Assessment Phase, a grueling four-day test that includes everything from chin-ups and push-ups to an exhausting 12-mile road march and a water survival test in which students climb along a rope that is suspended over water. The number of women dropped again in late May, when all eight failed the first phase for a second time, and Fivecoat awarded three of them the opportunity to become “Day 1 recycles.” The status is awarded to some service members who excel in many areas of Ranger School, but fail in a single key component.

On their third and final try, all three remaining women advanced, moving the gender assessment to the mountains. They reported July 11 to Camp Frank D. Merrill, a remote installation in the national forest leased by the Army. The women were joined by 156 male soldiers who had passed the first phase alongside them, and 42 men who already were training in the mountains, but had failed to pass there the first time.

The students arrived at Mount Yonah on Day 3 of training. Near the base of the Appalachian Trail, it is the site of at least two accidental civilian deaths since 2008 due to long falls from cliffs.

All but one of the soldiers completed the mountain road march, but it left many of them gasping for air by the time they reached the top. Afterward, instructors led them down a rocky, uneven trail toward a sheer rock wall perhaps 60 feet high. The students worked in pairs to climb it with the help of ropes, occasionally cursing as they slipped and a fellow Ranger student forcefully yanked a rope to stop their fall.

One of the women, perhaps 5-foot-5, made the climb quickly. A military police officer, she showed no signs of fear as she used a lane labeled as “Yellow.”

“You can tell she doesn’t even have muscle fatigue,” said Capt. Lesley-Anne Crumpton, one of four female “observer-advisers” the Army trained and deployed to the Mountain Phase in an effort to make sure the assessment goes smoothly. “I always watch for shaking. She didn’t even shake.”

The soldiers were soon faced with another challenge. A muscular thunderstorm swept through around noon, drenching uniforms and forcing the soldiers to seek cover from swirling winds and crackling lightning. Training continued afterward, with the newly created mud and wet stones forming additional obstacles as the soldiers practiced rappelling and eventually scaled a 150-cliff near the top of the mountain.

The Ranger students will begin a 10-day field exercise in the mountains next week. It includes simulated ambushes, night mountaineering, the use of rope bridges and patrols that are graded by instructors. It ends with a 200-foot rappel down a cliff at night aided by night-vision equipment. As of Thursday, 194 men and the three women were left in training.

In fiscal 2014, the average Mountain Phase class had 219 students. On average, 6 percent were dropped from Ranger School, 24 percent were recycled to try again and 70 percent moved on to the Florida Phase, Fivecoat said.

The chances of passing improve even more in the swamp. The average class there had 190 students in 2014, with 4 percent dropped, 19 percent recycled to take it again and 77 percent passing, Fivecoat said. The earlier portions at Fort Benning were the big obstacles. The average class had 369 students when beginning the initial Ranger Assessment Phase, with 44 percent dropped. The average class in the “Darby” phase that follows had 207 students, with 16 percent of students dropped, 27 percent recycled and 57 percent advanced to the mountains.