For the first time, three enlisted women have passed the Marine Corps’ grueling infantry course, carrying the same rifles and lugging the same 85-pound packs on the same 12-mile hikes through the piney woods of North Carolina as the men.

The female Marines are scheduled to graduate Thursday at Camp Geiger, N.C. — a historic development as the U.S. military prepares to open ground combat forces to women. But in a twist, the three women — identified Thursday as Pfc. Julia Carroll, Pfc. Christina Fuentes Montenegro and Pfc. Katie Gorz -- still won’t be allowed to serve in an infantry unit, at least not for a long while.

Marine Corps leaders say they need two more years to study whether it makes sense to allow women to serve as grunts. They note that no woman has passed the even more challenging infantry training course for officers (10 have tried). Before making a final decision, they said, they want to see many more female Marines try to pass the courses so the results can be evaluated.

“Any force-wide changes to be made will occur only after we have conducted our research, determined the way ahead and set the conditions to implement our recommendations,” Capt. Maureen Krebs, a Marine spokes­woman, said in an e-mail.

In January, after years of debate and legal challenges, the Pentagon announced that it would lift its long-standing ban on women serving in ground combat units by 2016, unless the armed services can justify why certain positions should remain closed. The decision was prompted in part by the recognition that women played a critical role in the wars in Afghanistan and Iraq, where commanders stretched rules to allow them to bear arms and support combat forces.

It remains an open question whether women will be allowed to try to become Army Rangers or Navy SEALs or artillery-shell loaders. Theoretically, if female troops prove that they can meet the same physical demands as those required of men, the doors are supposed to open.

Army leaders say they are developing “gender-neutral” standards for infantry and other combat forces and plan to eventually open those units to women, though they won’t rule out the possibility that they might decide to keep some off-limits.

Virtually all positions in the Navy and Air Force are accessible to women, with the exception of some elite commando teams.

For the Marine Corps, however, the biggest obstacle to integrating women into the infantry may be overcoming a deep-seated cultural resistance to the idea.

The Marines are the most tradition-­bound and male-
dominated of the armed services. Only 7 percent of the Corps is female, half the overall rate for the U.S. military.

In a survey last year, one in six male Marines said they probably would leave the service if they were forced to serve alongside women in ground combat units.

And although commanders say they are committed to giving women a fair chance, the Corps isn’t going out of its way to celebrate the fact that three female Marines passed the grinding training course for enlisted infantry. Marine officials rejected a request from The Washington Post to cover the graduation ceremony at Camp Geiger, saying that news coverage would be restricted to a few handpicked media outlets. They refused to identify the three female graduates until Thursday morning.

“The Marine Corps has a culture problem. There’s no doubt about it,” said Anu Bhagwati, a former Marine captain who serves as executive director for the Service Women’s Action Network, a group that advocates for female troops. “It’s the toughest climate for a woman to enter and succeed in.”

The infantry course is marked by long marches, obstacle courses and plenty of rifle practice. Instructors also teach grenade use, patrolling and how to avoid roadside bombs. Men and women train together, but the female Marines are housed in a separate barracks.

In September, 15 women joined 266 men at the outset of the course at Camp Geiger, where the Marines have trained for six decades.

Three women and 221 men made it through the two-month course and will graduate Thursday.

A fourth woman completed most of the hurdles but suffered a stress fracture in her leg that prevented her from taking her final physical fitness and combat fitness tests. She’ll be allowed to finish when she fully recovers, Marine officials said.

The male graduates will join infantry units right away. The women will have to take other jobs, though their successful completion of the course will be noted in their personnel files.

Rep. Loretta Sanchez (D-
Calif.), a member of the House Armed Services Committee, said it is unfair of the Marines to deny the women the right to join the infantry after they have proved themselves.

“I don’t believe there is a reason to exclude them now,” she said. “Certainly, there are many who thought women could not do this. But they’ve met all the standards that are existing today.”

Others said it would be a mistake to integrate the infantry without female officers or senior female noncommissioned officers to serve as mentors. So far, that barrier has not been breached. Over the past year, 10 women have tried without success to pass the Marine infantry officer course, which takes longer and is considered even more physically rigorous.

“It’s kind of backwards,” said Rep. Duncan D. Hunter (R-Calif.), a Marine combat veteran who has served in Iraq and Afghanistan. “If you don’t have any senior female leadership, it makes it hard.”

Officials with the Marine Corps and the Army said they won’t lower physical standards for combat troops to accommodate women. But Hunter said he was skeptical and suspected that the services might adjust requirements to make it easier to integrate units.

He also questioned whether many women really wanted to serve in the infantry, noting that only a handful of female Marine officers have sought to pass the course.

“If you only have 10 women who are interested, then what is the uproar all about?” he said. “It wasn’t a military push to do all this. It’s purely a political push.”

Statistics show that the overall pool of female Marine officers is small to begin with. Only about 140 female lieutenants are commissioned each year.

The first three female graduates of the enlisted infantry program are likely to have company soon.

Forty female Marines have started courses in the past few weeks. If the first co-ed training class is any guide, about one-quarter will endure to the end.