On July 30, 2016, then-Secretary of Defense Ash Carter lifted the ban on transgender troops serving openly in the military.
And with some taps of his fingers Wednesday morning, President Donald Trump started to roll that back.
In three tweets, Trump announced the U.S. government "will not accept or allow" transgender people to serve "in any capacity" in the armed forces.
The president says transgender service members are a burden to the military, due to the "tremendous medical costs and disruption that transgender in the military would entail."
Trump said he came to the decision after talking to generals and military experts, whom he did not name.
Trump did not say what will happen to transgender troops who are already in the military, and NBC News reports the Department of Defense is referring all questions to the White House.
So no one really knows yet how the ban might be put back in place.
Transgender individuals in the U.S. military
There aren't official figures publicly available for how many transgender service members are currently in the U.S. Armed Forces, the LA Times says.
A study by research organization RAND last year estimated there are between 1,320 and 6,630 service members on active duty who self-identify as transgender and an additional 1,500 or so in the reserves.
The American Civil Liberties Union says the figure is more like 15,500. (There are about 1.3 million troops total in the military.)
Not all of those transgender individuals will seek gender transition-related treatments. The RAND study estimated that each year, between 29 and 129 active duty service members seek transition-related care that could potentially disrupt their ability to deploy.
The cost of that could range from $2.4 million to $8.4 million, the study found. This makes up less than 1 percent of annual spending on active-duty health care.
As far as the relationships among service members, the RAND research indicates little or no impact on unit cohesion, operational effectiveness, or readiness. Some commanders involved in the study noted policy changes allowing transgender, gay and lesbian personnel to serve openly had benefits for all service members by creating a more inclusive and diverse force.
When Carter ended the ban, he gave the Pentagon a year to figure out how it would accept new transgender recruits into the military. The Pentagon was required to start accepting these recruits by July 1, 2017, Politico explains.
Currently Defense Secretary Jim Mattis delayed the July 1 deadline to give the military more time to evaluate “the readiness and lethality of our forces.” The delay only impacted new recruits, not those currently serving.
Under Mattis' orders, officials at the Pentagon have been studying how transgender troops in the military affect other service members, but not with a view toward removing transgender people from the military, several defense officials told the New York Times.
That's why the president's Twitter announcement is being described as "a surprise" and "shocking."
Here's what some of Minnesota's elected officials are saying on social media – so far it's been critical Democrats chiming in.