Updated: Thursday, July 27, 11:44 a.m.

Donald Trump’s Twitter decree banning transgender Americans from serving in the military because of the imaginary “tremendous medical costs” involved was framed by the president as the result of a deliberative process involving “consultation with my Generals and military experts.”

That seems to be far from the truth, given that a study conducted for the Department of Defense last year by the Rand Corp. showed that such costs would be minimal, and the announcement of the sweeping policy change, made while Defense Secretary Jim Mattis is on vacation, clearly caught the Pentagon by surprise.

The decree also came just three weeks after Mattis had ordered the armed forces to undertake a six-month review of the potential impact on the services of opening up recruitment to transgender individuals.

One of the authors of the Rand study, the Princeton economist Radha Iyengar Plumb, pointed out on Wednesday that the president’s claim about medical costs was not borne out by the evidence. Of an estimated 1,320 to 6,630 transgender personnel currently serving in the military, only a small subset — between 29 and 129 service members a year — would be likely to seek gender transition-related treatment that could disrupt their ability to deploy, Iyengar Plumb noted.

If the services were open to transgender recruits, the Rand study found, “health care costs would increase by between $2.4 million and $8.4 million annually, representing a 0.04 to 0.13 percent increase” in spending from the Pentagon’s $6 billion annual budget for medical costs for active-duty service members.

As Christopher Ingraham of the Washington Post reported, a considerably larger sum is spent by the Pentagon each year to treat erectile dysfunction.

As Matt Novak of Gizmodo noted, just five weeks ago, the chairman of the Joint Chiefs of Staff, Marine Gen. Joseph Dunford, publicly acknowledged that thousands of “transgender personnel are serving right now,” and reassured them that while the Pentagon was reviewing recruitment policy for the future, “there is no review ongoing that would affect the ability of those currently serving of serving.”

In the aftermath of Trump’s surprise announcement, Reuters reported, Gen. Dunford wrote to service chiefs, commanders, and senior enlisted leaders to say that the president’s tweet was not to be treated as an order. “There will be 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 guidance,” Dunford wrote, apparently establishing a precedent that the military does not consider Trump’s tweets to be official policy statements, despite explicit statements from the White House to the contrary. “In the meantime,” Dunford added, “we will continue to treat all of our personnel with respect.”

As part of that effort in May, the Pentagon produced inspirational videos for LGBT Pride month, including one about the struggle for acceptance by transgender personnel like Army Specialist Zane Alvarez.

Trump’s announced ban, however, went far beyond the question of new recruits, stating that “the United States Government will not accept or allow … Transgender individuals to serve in any capacity in the U.S. Military.”

So, if the information underpinning his decision to ban transgender soldiers is not coming from either military leaders or experts, where did the commander-in-chief get the wrong-headed idea that associated medical costs could bankrupt the Pentagon?

It is hard to say for sure, but the false claim closely echoes a meme promoted recently on social networks and in political advertisements targeting Democrats — and paid for by the Family Research Council, an ultra-conservative evangelical Christian group. The ads falsely suggest that the cost of Chelsea Manning’s hormone therapy was somehow equivalent to the cost of a war plane.

In a gleeful statement, Tony Perkins, the president of the Family Research Council and a former Marine, applauded Trump’s decision to reverse the Pentagon’s decision last year to allow transgender members to serve openly, which he called “the social experimentation of the Obama era that has crippled our nation’s military.”

Without citing any source for the statistic, Perkins went on to claim that having the Pentagon pay for gender transition-related treatment would mean “diverting billions of dollars from mission-critical training.”

Earlier this month, the House narrowly rejected an amendment to a nearly $700 billion spending bill to fund the Pentagon proposed by Rep. Vicky Hartzler, a Republican from Missouri, that would have blocked any of the money from being spent on medical treatment related to gender transition.

After Hartzler’s amendment failed, the Family Research Council lobbied against passing any Pentagon appropriations bill that allowed for spending on gender transition therapy, which could be what prompted Trump’s sudden decision.

“Now that we are assured that the Defense Department has its fiscal priorities in order,” Perkins said on Wednesday, “the Family Research Council withdraws our opposition to increasing the budget of the Department of Defense.”

Oddly, when Trump was asked during last year’s campaign if he would reverse the policy on transgender soldiers, during a discussion with retired soldiers hosted by Tony Perkins and another Christian extremist on the Family Research Council board, retired Lt. Gen. Jerry Boykin, he insisted that he would leave the decision “to the generals, the admirals, the people on top … and your top enlisted people.”

“We’ll get our military people to come back and make recommendations to me,” Trump said, “and I will follow those recommendations.”

Given how much of Trump’s information seems to come from Fox News, it seems likely that the president’s confusion and anger over the Pentagon’s acceptance of its transgender personnel might also have been stoked by Tucker Carlson, who expresses outrage over transgender issues on an almost nightly basis.

In recent weeks, Carlson has focused specifically on attacking the acceptance of transgender soldiers, calling the policy “a massive social program designed to affirm different communities because they put political pressure on the White House.”

“Most taxpayers like to think that the money the military spends goes to expenses like submarines and ammunition,” Carlson said at the start of another segment two weeks ago. “Very few think of sex changes and transgender awareness training,” he added. “The question is, will that help us win wars?”

Closing the feedback loop, Vice President Mike Pence is scheduled to appear on Carlson’s show on Wednesday night to discuss Trump’s decision to cancel the policy that so disturbed the pundit.

Top photo: President Donald Trump speaks to members of the U.S. military alongside Vice President Mike Pence following a meeting at the Pentagon in Washington on July 20, 2017.