WASHINGTON -- President Donald Trump has launched his second bid to oust all transgender troops from the military, and once again it will be headed to the courts to sort it out.

Although the new order will affect only a tiny fraction of America's 2.1 million service members, it has taken on oversized importance to Trump and his administration, who see transgender forces as a sign the military is “woke” or not focused on training and winning wars.

Defense Secretary Pete Hegseth, before he took the job, wrote in his book “War on Warriors” that “for the recruits, for the military, and primarily for the security of the country, transgender people should never be allowed to serve. It’s that simple.”

Trump's order to push out transgender troops, issued late Monday night, was instantly condemned by an array of activist groups as exceptionally egregious and ultimately harmful to military readiness. They say transgender people have been serving successfully for years, including openly on and off for the past decade.

Here's a look at what it all means and the confusing duel over the ban for the past decade.

Trump's order essentially says that anyone who is diagnosed with gender dysphoria — the unease someone has when their assigned sex and gender identity don’t match — cannot serve in the military. It gives the defense secretary 60 days to update the medical standards for enlistment and re-enlistment to reflect that change. And it gives Hegseth 30 days to lay out how he plans to implement it all.

According to the order, “expressing a false ‘gender identity’ divergent from an individual’s sex cannot satisfy the rigorous standards necessary for military service.” It says the hormonal and surgical needs involved in taking on a different gender identity “conflicts with a soldier’s commitment to an honorable, truthful, and disciplined lifestyle."

It concludes that, “A man’s assertion that he is a woman, and his requirement that others honor this falsehood, is not consistent with the humility and selflessness required of a service member.”

The order also zeroes in on the heady bathroom issue.

On his first day in office Trump issued an executive order that he said would “restore biological truth” to the federal government by eliminating the word “gender” and replacing it with “sex.” He said the federal government will only recognize people based on their sex at the time of conception based on their “reproductive cell.”

His latest order expands on that, saying the military will “neither allow males to use or share sleeping, changing, or bathing facilities designated for females, nor allow females to use or share sleeping, changing, or bathing facilities designated for males.”

The Pentagon has said in recent years that it is impossible to count the total number of transgender troops. The military services say there is no way to track them and that much information is limited due to medical privacy laws.

Estimates have hovered between 9,000 and 12,000. But it will be very difficult for officials to identify them, even as service members worry about the hunt to root them out.

“This casts an enormous shadow on people that are getting ready to go on a deployment for six months overseas or, you know, getting ready to go on a combat mission,” said Sasha Buchert, counsel for Lambda Legal. “This is going to be extremely disruptive. And they’re going to have to look over their shoulder in fear of when the next shoe will fall.”

Since transgender troops have been able to serve openly for a number of years, it’s possible their fellow unit members or commanders know who some of them are. That triggers worries about people identifying them in order to get them pushed out — and raises parallels to the Clinton administration's Don't Ask, Don't Tell policy, which allowed gays to serve in the military as long as they didn't “tell.”

In March 2018, then-Defense Secretary James Mattis released a memo with unprecedented details on the number of transgender forces and how many of them had sought mental health help or were planning to seek surgery.

It said, at that time, there were 8,980 service members who identified themselves as transgender, and 937 had been diagnosed with gender dysphoria. The report said data collected by the military health system revealed that 424 of those service members diagnosed had gotten treatment plans approved and for at least 36 of them those plans didn't include “cross sex hormone therapy or sex reassignment surgery.”

In 2015, then-Defense Secretary Ash Carter broached the idea of lifting the ban on transgender troops and allowing them to serve openly, which raised concerns among military leaders. He set up a study, and then about a year later, in June 2016, announced the ban was ended.

A year after that, just six months into his first presidential term, Trump suddenly announced via tweet he was not going to allow transgender people to serve in the military “in any capacity.” The tweets caught the Pentagon by surprise and plunged leaders into what became a roughly two-year struggle to hammer out the complex details of who would be affected by the ban and how it would work, even as legal challenges poured in.

By March 2019, as courts ruled against the ban, the Pentagon laid out a policy that allowed those currently serving to continue with plans for hormone treatments and gender transition if they had been diagnosed with gender dysphoria. But it barred new enlistments of anyone with gender dysphoria who was taking hormones or had transitioned to another gender. And it said in the future those diagnosed with gender dysphoria must “serve in their birth gender” and were barred from taking hormones or getting transition surgery.

Soon after President Joe Biden took office in 2021, he overturned Trump's ban and the Pentagon also announced it would cover transition medical expenses for troops.

The chiefs of all four military services told members of Congress in 2018 they were seeing few problems as transgender troops began serving openly.

The Navy chief at the time, Adm. John Richardson, said the Navy was dealing with the issue the same way it handled the integration of women sailors on submarines.

And the Marine commandant then, Gen. Robert Neller, said there were no unit cohesion or discipline problems. His only concern, he told a Senate committee, was that some commanders were saying they had to spend “a lot of time” with transgender people as they worked through medical requirements involving their transition to their preferred gender.

Sarah Klimm, a transgender Marine who served for 23 years, retired just as the end to the ban was announced in 2016, so was never able to serve openly.

”Trans military members that are out there right now are dropping bombs, pulling triggers, fixing all the weapons systems,” she said Tuesday. “And now you’re looking to keep them away.”

Klimm, who is now a policy analyst for Minority Veterans of America, said it’s an especially precarious time to remove thousands of service members as recruiting has been a struggle.

Emily Shilling, who has been openly transgender since 2019, is currently serving as a commander in the Navy with more than 19 years of service, including as a combat pilot who flew 60 missions in the Iraq and Afghanistan wars.

“I just want to continue serving my country, using the skills this nation invested in me as a fighter pilot and leader,” she said, stressing that she was speaking in her personal capacity. "For nearly two decades, I’ve upheld the highest standards of excellence, leading teams in combat and peace. All I ask is the opportunity to keep using my training and experience to serve this country with honor, courage and dedication.”

___ Associated Press writer Tara Copp contributed to this report.