Women in a new Marine Corps unit created to assess how female service members perform in combat were injured twice as often as men, were less accurate with infantry weapons and were not as good at removing wounded troops from the battlefield, according to the results of a long-awaited study produced by the service.

The research was carried out by the service in a nine-month experiment at both Camp Lejeune, N.C., and Twentynine Palms, Calif. About 400 Marines, including 100 women, volunteered to join the Ground Combat Element Integrated Task Force, the unit the Marine Corps created to compare how men and women do in a combat environment.

“This is unprecedented research across the services,” said Marine Col. Anne Weinberg, deputy director of the Marine Corps Force Innovation Office. “What we tried to get to is what is that individual’s contribution to the collective unit. We all fight as units. … We’re more interested in how the Marine Corps fights as units and how that combat effectiveness is either advanced or degraded.”

The study, an executive summary of which was released Thursday, was carried out as all the services prepare to submit recommendations to Defense Secretary Ashton Carter this fall on whether any jobs should be kept closed to women. In a landmark decision in January 2013, then-Defense Secretary Leon Panetta rescinded a decades-old ban on women serving in combat jobs like infantry, but gave the services until this fall to research how they wanted to better integrate women and if any jobs should be kept closed.

The Pentagon faces increasing pressure to fully integrate women, following the historic Aug. 21 graduation of two female officers from the Army’s Ranger School.

The legendarily difficult school was opened on an experimental basis this spring, with 1st Lt. Shaye Haver, 25, and Capt. Kristen Griest, 26, completing the requirements. Sixteen other women who attempted the course failed, while one other woman remained in the school’s third and final phase at Eglin Air Force Base as of last week.

The Marine Corps’ research will serve as fodder for those who are against fully integrating women. It found that all-male squads, teams and crews demonstrated better performance on 93 of 134 tasks evaluated (69 percent) than units with women in them. Units comprising all men also were faster than units with women while completing tactical movements in combat situations, especially in units with large “crew-served” weapons such as heavy machine guns and mortars, the study found.

Infantry squads comprising men only also had better accuracy than squads with women in them, with “a notable difference between genders for every individual weapons system” used by infantry rifleman units. They include the M4 carbine, the M27 infantry automatic rifle and the M203, a single-shot grenade launcher mounted to rifles, the study found.

The research also found that male Marines who have not received infantry training were still more accurate using firearms than women who have. And in removing wounded troops from the battlefield, there “were notable differences in execution times between all-male and gender-integrated groups,” with the exception being when a single person – “most often a male Marine” – carried someone away, the study found.

The gender-integrated unit’s assessment also found that 40.5 percent of women participating suffered some form of musculoskeletal injury, while 18.8 percent of men did.

Twenty-one women lost time in the unit due to injuries, 19 of whom suffered injuries to their lower extremities. Of those, 16 women were injured while carrying heavy loads in an organized movement, like a march, the study found.

The full study is more than 1,000 pages long, Marine officials said. They anticipated publishing it online in coming days.