President Donald Trump has reportedly formally given Defense Secretary Jim Mattis six months to fully implement his new ban on transgender troops. Roughly one month after the president’s initial announcement, reports emerged that the White House delivered the Pentagon a two-and-a-half-page memo calling on the military to cease admitting transgender recruits. The memo also appears to give Mattis some discretionary authority to decide the fate of those currently serving.

The ban comes on the heels of Trump unveiling his plan for the Afghan War—the longest conflict in American history—which calls for an open-ended troop commitment. As the U.S. military renews its efforts to hunt ISIS and thwart North Korea, it will need more able-bodied troops to meet these sprawling commitments. But finding them is becoming increasingly difficult.

In December 2015, the Harvard Institute of Politics released the results of a survey of Americans aged 18 to 29 that gauged their views on military policy. Researchers found that 60 percent of millennials quizzed supported committing U.S. combat troops to fight ISIS in Syria and Iraq, but that an almost equal number—62 percent—said they would “definitely not” join the fight personally. An additional 23 percent would “probably not” sign up to serve, leaving only 15 percent actually willing to participate in such an effort.

What’s more, the 2016 iteration of an annual survey by Blue Star Families found that, after years of open-ended warfare, 57 percent of active duty families says they wouldn’t recommend military careers to their children. Despite a wide range of military engagements, Americans are seemingly less interested than ever in military service. Thus, it’s an odd time to shun any number of the select few Americans who still are.

Many American allies already allow transgender troops to serve openly, including Israel and most of the NATO alliance.

Trump first announced his intentions in a series of tweets on July 26, 2017, declaring that the government would no “allow transgender individuals to serve in any capacity in the U.S. military.” He cited conversations with his generals for his reasoning. Nevertheless, those generals were as surprised as everyone else. Pentagon officials had received no warning of the tweet and told reporters and lawmakers that they would not act until the White House provided formal guidance.

“No modifications to the current policy until the President’s direction has been received by the Secretary of Defense and the Secretary has issued implementation guidelines,” Chairman of the Joint Chiefs of Staff Joseph Dunford wrote in a memo, circulated throughout the Pentagon the day after Trump’s tweet. “In the meantime, we will continue to treat all of our personnel with respect.”

Trump has insisted transgender troops come with too many medical expenses and cause “disruption.” The Obama administration ended regulations barring transgender persons in June 2016 and directed the Pentagon to study extending health benefits, including care related to gender reassignment, to transgender troops. But many had already transitioned on their own dime and still others wouldn’t seek the procedure.

If the Pentagon extended transgender troops benefits, a 2016 Rand Corporation study estimated it would spur a maximum annual increase in health care costs of $8.4 million. By even the highest estimates, that’s less money than the military health care system already spends on Viagra.

The Rand study also looked of other countries with trans troops. Many American allies already allow transgender troops to serve openly, including Israel and most of the NATO alliance. Rand found that none of those country’s militaries experienced any “significant effect on cohesion, operational effectiveness or readiness” when transgender troops began serving openly.

The British military opened its ranks to transgender recruits 17 years ago. There, the military “encourages those who have not yet started their gender transition to complete their transition before joining,” Rand noted. Nevertheless, the British military will sometimes cover the costs of hormone replacement therapy, though not transition surgery. Leaders work with troops to accommodate transitioning soldiers but may discharge them if the process begins to take too long or interfere with duties.

The Israeli Defense Force (IDF) recently formalized its transgender policy in 2013. Israel doesn’t allow individuals to start gender reassignment surgery until the age of 21. Most Israeli conscripts are either finished serving or are preparing to separate, so most transgender troops in Israel are career soldiers. Combat units are off-limits to those going through the transition period, but are open once a recruit has finished and meets the physical requirements. The Israeli military pays for the transition, which isn’t particularly remarkable given that Israel has universal health care.

Military figures around the world swiftly reacted to Trump’s first announcement. The Canadian military trolled Trump by proudly tweeting photo of sailors marching in a Pride event with a message that Canadians of all genders and orientations are welcome to join. Rear Admiral Burton, the Commander of the U.K.’s Maritime Forces, tweeted an article about Trumps tweets from his own official account, adding that he was “glad we are not going this way.”

In an interview with Israeli Army Radio, lawmaker and former commander of IDF Manpower Command Elazar Stern bluntly stated that allowing transgender troops was a no-brainer for him. “It makes us strong that we don’t waste time on questions like this,” Stern said. “It’s something to be proud of.”

Opinion among U.S. military brass has always been divided. Senior officers in all branches have expressed a mix of support, opposition and indifference to a ban. Dunford was a known skeptic of transgender troops but still seemed agitated by Trump’s surprise directive and disregard for proper channels. On August 1, 56 retired generals and admirals released a letter that branded the transgender ban a mistake that would hurt military readiness.

The strongest words from a serving American officer came from Coast Guard Commandant Admiral Paul Zukunft. The Coast Guard technically operates under the Department of Homeland Security, but is also a military branch and as such would be subject to the ban. Zukunft took his stance much further than other service chiefs in remarks that many observers interpreted as a rebuke.

“The first thing we did is we reached out to all 13 members of the Coast Guard who have come out [as transgender],” Zukunft told a crowd of attendees while visiting a Washington think tank on August 1. He reached out personally to Lt. Taylor Miller, the Coast Guard’s first openly transitioning officer, who was featured in the Washington Post in July.

“If you read that article, Taylor’s family has disowned her … and I told Taylor, I will not turn my back. We have made an investment in you and you have made an investment in the Coast Guard and I will not break faith,” Zukunft said. “And so that was the commitment to our people right now. Very small numbers, but all of them are doing meaningful Coast Guard work today.”

Regardless of what Mattis thinks, he doesn’t have wiggle room to digress now that he’s received direct orders.

Zukunft also said that following the president’s tweet, he personally reached out to Mattis and then Secretary of Homeland Security John Kelly—both retired Marine generals—and urged them to consider the announcement’s implications.

With the orders official, all eyes are now on Mattis. He is perhaps the most popular figure in the Trump administration, with broad support from both Democrats and Republicans and a near-mythic status among many veterans. He’s known to lean right in his personal politics, but is generally regarded as a non-partisan figure.

While on active duty, Mattis expressed skepticism toward both repealing the “Don’t Ask, Don’t Tell” policy and opening combat units to women. However, during his January confirmation hearing he seemed to have significantly softened both stances. “If someone brings me a problem, I’ll look at. But I’m not coming in looking for problems,” Mattis told senators. “I’m looking for ways to get the department so it’s at its most lethal stance.”

Trump’s tweets went out while Mattis was on vacation. The New York Times reported he was apparently “disgusted” by Trumps tweets when he learned of them. Much like Dunford, his annoyance was likely more a result of the president’s lack of warning. “We are going to study the issue,” Mattis told reporters at the Pentagon when he returned to work in on August 14. “There’s a host of issues and I’m learning more about this than I ever thought I would and it’s obviously very complex to include the privacy issues which we respect.”

Mattis seems to have little interest in taking sides in the culture wars embroiling the nation. He’s far more concerned with the physical wars that have troops fighting and dying in foreign lands. Regardless, anything that happens will have domestic political consequences. The Trump campaign seems to be counting on that. Not long after the first tweets, a White House official told Axios’s Jonathan Swan that “this forces Democrats in Rust Belt states like Ohio, Michigan, and Wisconsin, to take complete ownership of the issue.”

LGBT activists are already taking the fight to the judicial branch. Earlier this month, the National Center for Lesbian Rights and GLBTQ Legal Advocates & Defenders filed a lawsuit on behalf of five unnamed transgender people in the military in Washington, D.C., arguing the ban is unconstitutional.

In the meantime, regardless of what Mattis truly thinks, he doesn’t have much wiggle room to digress now that he’s received direct orders from the commander-in-chief. It remains to be seen how transgender troops currently serving will fair under his leadership; their fate is far from settled.