"Our military...cannot be burdened with the tremendous medical costs and disruption that transgender in the military would entail," Trump said on Twitter

President Donald Trump announced a sweeping ban on transgender people serving in the military in a series of tweets early Wednesday – reversing an Obama Administration policy to allow transgender service members to serve openly.

The president’s statement claimed transgender service members – who were only permitted to serve openly a year ago – burden the military with “tremendous medical costs” and “disruption.”

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“After consultation with my Generals and military experts, please be advised that the United States Government will not accept or allow Transgender individuals to serve in any capacity in the U.S. Military,” he wrote.

“Our military must be focused on decisive and overwhelming victory and cannot be burdened with the tremendous medical costs and disruption that transgender in the military would entail,” Trump continued. “Thank you.”

Ironically, Trump’s announcement comes precisely 69 years after President Harry S. Truman signed executive order 9981 on July 26, 1948, establishing equality of treatment and opportunity in the Armed Services and leading to the end of segregation in the services.

A 2016 study by the RAND Corporation estimates there are up to 6,630 active duty transgender service members. It also determined that the cost of extending gender reassignment benefits to services members would cost the Pentagon between $2.4 million and $8.4 million a year – a tiny fraction of the military healthcare budget.

Then-Defense Secretary Ash Carter, who served under President Barack Obama, announced last June that transgender men and women would be allowed to serve in the military – and set a one-year deadline for the Pentagon to come up with a plan to integrate the services.

“Our mission is to defend this country, and we don’t want barriers unrelated to a person’s qualification to serve preventing us from recruiting or retaining the soldier, sailor, airman or Marine who can best accomplish the mission,” Carter said at the time. “We have to have access to 100 percent of America’s population for our all-volunteer force to be able to recruit from among them the most highly qualified — and to retain them.”

Carter’s Pentagon issued a 71-page implementation handbook to help guide service members and commanders through issues connected to transgender service. The handbook addresses a range of issues including transition, deployment, physical and medical readiness, bullying, social events, and the proper attire during a swim test.

The primary takeaway for commanders is that they “are responsible for the collective morale and welfare and good order and discipline of the unit and for fostering a command climate where all members of your command are treated with dignity and respect.”

Earlier this year, Trump’s Defense Secretary, James Mattis, delayed the implementation of the Obama plan by six months. Trump’s announcement comes one day before the military’s deadline to update its medical standards to accommodate transgender service members.

Carter responded to the ban in a statement on Wednesday.

“Quality people in uniform are what make our military the finest fighting force the world has ever seen,” he said. “I continue to maintain that what matters in choosing those who serve is that they are best qualified. To choose service members on other grounds than military qualifications is social policy and has no place in our military.”

He continued, “There are already transgender individuals who are serving capably and honorably. This action would also send the wrong signal to a younger generation thinking about military service.”

Joshua Block, the ACLU’s senior staff attorney, quickly followed up with tweets asking transgender service members to contact him.

“If you are a trans service member or reservist please contact me,” he wrote. “If you know a trans service member or reservist tell them to contact me.”

The Anne Frank Center for Mutual Respect, who says their mission is to “work for Anne’s dream of no prejudice,” released a statement and said they are “sickened” by Trump’s announcement.

“This move by President Trump is unconscionable evil,” said executive director Steven Goldstein. “Rarely if ever in our nation’s history has a President made a move like this that so drastically reverses the civil right gains of an oppressed community.”

In response to a tweet asking Utah lawmakers if they stand with transgender people from the state, Sen. Orrin Hatch replied, “Yes.”

Hatch, a Republican, has voted to protect LGBT people from housing and employment discrimination based on sexual orientation or gender identity in Utah, where much of the population are practicing Mormons.

Trump’s announcement was immediately met with outrage and confusion on social media and beyond.

“The President’s tweet this morning regarding transgender Americans in the military is yet another example of why major policy announcements should not be made via Twitter,” McCain said as part of a lengthy statement.

His comments were echoed by a Pentagon source who tells PEOPLE: “When the policy changed last year to allow transgender people to serve, all of us here saw it coming. We were prepared. We were not prepared to read on Twitter that the policy is being reversed. Everyone has questions.”

Queer YouTube star Kaitlyn Alexander added, “Trans people are not burdens. Countless Trans people have given their lives for their country. This is unacceptable.”

“So, biggest baddest most $$ military on earth cries about a few trans people but funds the F-35?” Manning wrote on Twitter. “Sounds like cowardice.”