Army and Marine Corps leaders swapped pledges with members of the Senate Armed Services Committee on Tuesday not to cave to political pressure and relax ground combat skill requirements so that more women will qualify to serve in infantry, armor and Special Forces units.

Certainty that such pressure will come, and need to be resisted to protect combat effectiveness, was expressed both by senators and witnesses during the first congressional hearing held to review how the Army and Marine Corps plan to open all ground combat jobs to women.

No senator on the committee suggested Congress should block the Dec. 3 order from Defense Secretary Ash Carter to open the most brutal jobs in the military to women who meet gender-neutral standards for each skill. Indeed, the clear consensus was that no woman should be denied access to any military job based only solely on gender.

But many on the committee echoed in some way the caveat for supporting of full gender integration that Gen. Mark A. Milley, Army chief of staff, declared in his opening statement.

Gender integration will “sustain or improve the overall readiness [and] capability of the force — if, and only if, we maintain and enforce rigorous combat-readiness standards, we remain a merits-based, results-oriented organization, and we apply no quotas and no pressure. We cannot compromise combat readiness and effectiveness for any reason whatsoever.”

“One thing is inviolate,” said Navy Secretary Ray Mabus. “Standards can never be lowered for any group or for any job.”

Gen. Robert B. Neller, commandant of the Marine Corps, echoed that point but also warned the unknowns of full gender integration are many.

“I have concerns about retention. I have concerns about injury rates. I have concerns about propensity to re-enlist [and] career progression. I have concerns about what’s going to happen if the [female] numbers are low, because they probably will be at the beginning,” Neller said.

Neller and Milley also emphasized that despite an April deadline to begin full integration of women into ground combat jobs, it could take years, perhaps even a decade, to complete if the services proceed with the care needed to ensure no lapse to fighting effectiveness or unit cohesion. That go-slow approach resonated with senators who have some military experience.

It was three years ago that then-Defense Secretary Leon Panetta announced that every military job would be opened to women who could qualify unless, after a period of study, a strong readiness case could be made to grant job or unit exemptions. Since then the Army and Marine Corps worked to assess the physical and readiness impacts of integrating women into their ground elements, relying in part on special field studies.

The Army study simulated tasks to determine gender-neutral standards for each military occupational specialty based on physical tasks. A Marine Corps task force on gender integration went farther, simulating a combat environment with men and women Marines living and working together. More than 400 female volunteers received combat skill training and became part of mixed-gender squads, teams and crews. Their performance under combat-like conditions was tracked for five months against male-only units. By almost every measure — speed, firing accuracy, incidence of injury, physical endurance — all-male units performed better.

Within a day of receiving the 1,000-page Marine Corps report last September, Mabus gave a newspaper interview to criticize the study as flawed, focusing too heavily on average performance of women and too little on capabilities of outstanding female Marines.

Marine Corps leaders defended the study and requested that some frontline ground combat skills and units be exempt from gender integration. In December, Carter rejected the request, ordering all services immediately to draft plans to implement gender integration across all skills.

At the hearing Mabus was upbraided by the committee’s chairman, Sen. John McCain, R-Ariz., and several colleagues.

The service studies “demonstrated that biological differences between men and women can have implications when it comes to the sustained physical activities involved in combat,” said McCain. “Rather than honestly confront these realities, some have sought to minimize them.”

McCain tagged Mabus are the lead critic, saying he disparaged the study, and even questioned the caliber of female Marines who participated, within a day of the study’s release and without having read it.

Sen. Daniel Sullivan, R-Alaska., a Marine Corps Reserve infantry officer, joined in berating Mabus, saying the secretary and not the Marines had an agenda. Sullivan also attacked Mabus for ordering Neller on Jan. 1 to develop a plan to gender integrate recruit training by Jan. 15. Sullivan called it “an outrageous and ill-advised order” impossible for the Corps to carry out.

“It was not only possible but the Marines met that,” Mabus told him, explaining he got a full briefing by Jan. 14.

When Sullivan asked Neller his opinion of the order, Neller had to contradict Mabus, saying the briefing on the 14th wasn’t a plan to shift to gender-integrated training but an explanation of current basic training and why Marines want to continue to train men and women recruits separately.

McCain told Mabus he “complicated the whole situation for those of us who fully support the integration of women in the military.”

Five days earlier, Mabus had another setback. Carter, in announcing a series of family support initiatives, announced a doubling of maternity leave, to 12 weeks, for Army and Air Force women. Navy and Marine Corps women also will get 12 weeks maternity leave, but that would be six weeks less than they are allowed now.

Last year Mabus grabbed the lead on this issue, granting new moms in Navy and Marine Corps 18 weeks of maternity leave back to last January. Air Force announced in December it would follow the Navy’s lead — until Carter set 12 weeks’ maternity leave for all services, an unusual benefit rollback.

Sailors and Marines currently pregnant or who become pregnant within 30 days of Carter’s policy change will still be eligible for the full 18 weeks.

“We’re glad we enabled a conversation for the entire Department of Defense on this very important topic, and now all servicemembers will receive 12 weeks of maternity leave,” said a Navy spokesman.

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