“We don’t accomplish our mission without every service member showing up to give their all,” he said. If a member of a team is suddenly distracted by fear of losing their job, their career, and their mission in life, that detracts from the mission. If everyone else on their team is worried about them, that’s an even bigger distraction.

The United States Navy trains its officers to lead men and women under extreme duress, to buck them up with a calming voice in the horrors of war. He said his commander told him Wednesday that a lot of transgender service members around the world would be looking to him to be that calming voice. “Go do that.”

Thursday got better. The Pentagon issued two stunning directives, announcing that nothing would change unless the president notified the secretary of defense, who in turn would need to issue formal guidelines. That was reassuring, Peace said, and validated her chain of command’s decision to back her. “But I’m still pretty worried,” she said this weekend.

Captain Peace wondered who else was on edge. “How do you feel safe if we can take a class of people that have been serving openly and serving honorably and say, ‘You can’t serve anymore’? Then who’s next? Is it gays and lesbians? Is it women? Blacks? Muslims? Atheists? At any moment, it might be you that’s told you’re not qualified to serve any longer, either.”

Before he was Blake, Dremann was serving in a submarine as a woman, convinced his closet was securely locked. Then he transferred to the Pentagon in 2015. About three days in, a female lieutenant colonel pulled him aside and asked, “Is there another name you go by outside of work?”

He was alarmed. He confessed the full story, but asked how she knew. “You don’t exactly present as a female,” she said. Oh. She had been doing some reading, Dremann said.

“My previous command on an all-male submarine didn’t have a clue,” Dremann said. “It was 2013—people barely knew what transgender was. When my voice dropped, they just figured it was my cigarette smoking. Testosterone? Not how people react.”

The lieutenant colonel called Dremann back an hour after their Pentagon conversation. She said the division had discussed it and, if he was O.K. with it, they would like to call him Blake.

Active Duty Navy Lieutenant Commander, Blake Dremann Photograph by T.J. Kirkpatrick.

The general perception is that Congress freed gays to serve when it repealed Don’t Ask, Don’t Tell, but that isn’t quite accurate. All it did was repeal its own prohibition on gays, returning to the status quo, where the president and his commanders exercise unfettered authority.

The policy of expelling homosexuals from the U.S. military dates back to the 18th century. General George Washington ordered Lieutenant Gotthold Frederick Enslin literally drummed out of the Continental Army for copulating with a private in his cabin. A solemn disgracement ceremony was conducted on the Valley Forge Grand Parade, where Enslin’s sword was broken in half over his head and he was marched out, as drummers and fifers beat a slow dirge.

For most of the ensuing 215 years, American presidents chose to exercise their discretion against the L.G.B.T. community. There was only one anomaly where Congress intervened—the 17 years of Don’t Ask, Don’t Tell. It forbade the president from allowing known homosexuals, but didn’t actually mention transgender members of the military. When Congress rescinded that law in 2010, it returned to silence. President Obama had no more or less authority over those who identified as L.G.B.T. than any of his predecessors prior to 1993. But he was the only one to use it to protect them. Trump was the second, until Wednesday.