The United States Marine Corps, it seems, won’t go down without a fight on fully integrating women.

As the only branch to air its opposition to the Pentagon’s plan to allow women into even combat jobs such as infantry, the Marines have seemingly found themselves in a new chapter of the gender integration struggle: boot camp.

The Marine Corps, like the Army, Navy and Air Force, was required to submit to the Pentagon a detailed plan outlining how they would fully integrate the genders, with the goal of executing those plans no later than April 1. But the Marines, the only service that segregates men and women in basic training, turned in a plan that left out any changes relating to boot camp, likely because there was no explicit directive for them to do so. Additionally, a set of guidelines released with Pentagon’s directives indicated that the branches would use existing training procedures when implementing the changes.

So the Marines are being nudged to do more.

Earlier this month, Secretary of the Navy Ray Mabus sent a memo to Gen. Robert B. Neller, the commandant of the Marine Corps, notifying him that the Marines had 15 days to submit a detailed plan that would address gender integration in basic training.

“Officer and enlisted basic training is the first opportunity to develop the cohesion needed for full integration of women in the Armed Forces,” said a senior defense official with knowledge of the situation. “Secretary Mabus has directed the Marine Corps to submit a plan to integrate training during this critical milestone in the development of new Marines.”

Lt. Col. Eric Dent, Neller’s spokesman, said the Marines submitted their gender integration plan on Dec. 17 and received additional memos regarding boot camp integration dated Jan 1 shortly after.

“We’ve received the [Secretary of the Navy’s] additional guidance and we’re reviewing it,” Dent said.

The Marine Corps currently operates two enlisted recruit training depots, one in San Diego, Calif., and one on Parris Island, S.C. Parris Island, however, is the only location that currently trains female recruits at a separate battalion known as the 4th Recruit Training Battalion (the male battalions are 1st, 2nd and 3rd). It is unclear if the depot in San Diego will soon accept female recruits. The Army, however, integrates women at the platoon level — as it has since the mid 1990s — when it comes to basic training. The Air Force started integrating basic training in 1977, while the Navy did the same in 1992.

In a Wednesday Marine Corps Times article, a Marine official was quoted as saying that the 15-day deadline to come up with a plan for boot camp integration was “an aggressive time frame,” but officials with knowledge of the situation say that plans to integrate Marine Corps boot camp have long been part of the discussion — it was just never explicitly written in any prior directives.

“The memo directing a plan for boot camp integration codifies discussions that had been going on for months….. so it was not a surprise,” the official said, who requested anonymity to speak candidly about the matter.

In light of the news, Marines and Marine veterans took to social media, some voicing support for the new plan, while others were against it.

The debate for a gender-integrated basic training in the Marine Corps has been a longstanding one. Many argue that separating male and female recruits from the get-go imbues a pervasive ideology of gender segregation throughout individual Marines’ careers, while others believe that keeping recruits separate is an old and effective tradition.

Currently at Parris Island, while male and female units train separately, there are varying degrees of integration. According to an active duty drill instructor who spoke on the condition of anonymity because he had not been authorized to speak publicly about the matter, female and male recruits take classes together and often interact if they are “on deck” at the same time during large events like the Crucible and Basic Warrior Training week. This is a relatively large shift from years past when the only interaction a male recruit might have with a female is during church services on Sundays.

“The thing is how much more integrated can we get? We already train with females,” the drill instructor said. “What do they want? Them to live in the same squad bay? Cause that ain’t going to happen.”

This post has been updated