An enlisted female student at the Infantry Training Battalion carries another female student during the movement-under-fire portion of the Combat Fitness Test at Camp Geiger, N.C., on Sept. 26. The Marine Corps has continued to face scrutiny as it gradually expands the scope of its research into which jobs women should fill in combat. (Marine Corps photo by Cpl. Chelsea Flowers Anderson)

Three female Marine Corps officers on Thursday passed the grueling combat endurance test that kicks off the service’s screening for infantry officers, paving the way for the first woman to potentially graduate from the program.

The test is conducted at Quantico, Va., and is designed to assess each individual’s ability to withstand exhausting physical conditions and make difficult decisions at the same time. Twenty-four female volunteers have attempted the Marine Corps’ Infantry Officer Course, but none have passed to date. One woman passed the initial endurance test in 2012, but was dropped from the course about a week later due to stress fractures in her foot.

The integration of women at the Infantry Officer Course is one of the high-profile parts of the Pentagon’s ongoing research into which new jobs women should be allowed to serve in while in combat units. The infantry officer course that began Thursday included 93 men and seven women, said Capt. Maureen Krebs, a Marine Corps spokeswoman. Sixty-seven men passed along with the three women, and will continue through training.

Two of the women who passed the combat endurance test Thursday are captains who volunteered, Marine officials said. The third is a female lieutenant who attempted the course in July and did not pass, but opted to try again. The Marine Corps will not release their identities, citing federal guidelines for conducting human research.

The women who passed Thursday did so after Marine Corps leaders decided in July to open the Infantry Officer Course to active-duty female officers who are “company-grade,” including not only new lieutenants, but seasoned ones and captains, too. Those who volunteer were required to meet a new requirement: Completion of the male version of the service’s annual Physical Fitness Test and the Combat Fitness Test with first-class scores.

If the women pass the infantry course, they still will not be allowed to join the infantry. The Infantry Officer Course was opened on an experimental basis, and the job itself remains closed to women, Marine officials said.

Critics of opening the all-male infantry say doing so would weaken it. They cite privacy issues, and raise questions about whether political correctness would pave the way for a relaxing of standard. They also bring up cultural issues about whether men and women can work together effectively in high-stress situations. Others say women, if given the chance, will prove they can serve with distinction in the infantry, and that integrating them could help alleviate long-term problems in the military like sexual assault

Other services also are grappling with how to expand the integration of women in the military. Army Ranger School, for example was opened on experimental basis for the first time to women this month. They have until Dec. 1 to volunteer, and will do so on a one-time basis only, Army Col. Linda Sheimo told reporters at a conference on Friday.