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, Georgia. 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.

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.