Defense Secretary Ashton B. Carter on Thursday announced the Pentagon has lifted a ban on transgender people serving openly in the military, effective immediately.  

The policy change, which will take a year to implement fully, will allow the military to avail itself of “all talent possible” to remain the best fighting force in the world, Carter said.  

Carter, who first ordered a review of the issue last July, said allowing transgender individuals to openly serve is a matter of principle. But he also stressed that the military would not change its standards for those members who are transgender.    

“Americans who want to serve and who can meet our standards should be afforded the opportunity to compete to do so,” Carter said.  

Carter acknowledged that military leaders had some concerns about the implementation plan, which the defense secretary tweaked to address those concerns.  

Within the next 90 days, the department will roll out guidebooks to commanders and doctors on transgender service. Military treatment facilities will begin all medically necessary care for transgender members, who have had to seek private care and pay out of pocket for health issues related to their gender identity.  

A Rand Corp. review determined that health care costs associated with the policy change would be “minimal” because of the small population affected.  

The study estimates the number of transgender individuals currently serving on active duty at between 1,320 and 6,630 out of a total of about 1.3 million service members — and not all of those transgender service members would seek medical treatment or become medically nondeployable.  

Rep. Sean Patrick Maloney, the first openly gay member of Congress from New York, applauded the Pentagon’ “monumental decision”  

“Although some may disagree with this decision, the military has always been the site of social progress. From requiring racial integration over a decade before the rest of the country – to allowing women in combat roles – the military has been the site of proactive social integration for much of our nation’s proud history,” he said.  

But the policy change drew fire from some Republicans on Capitol Hill.  

House Armed Services Chairman Mac Thornberry , R-Texas, quickly released a statement accusing the president of prioritizing politics over policy, calling into question whether transgender people can deploy overseas.  

“Our military readiness — and hence, our national security — is dependent on our troops being medically ready and deployable,” Thornberry said in a statement. “The administration seems unwilling or unable to assure the Congress and the American people that transgender individuals will meet these individual readiness requirements at a time when our Armed Forces are deployed around the world.”  

Over the next several weeks, Thornberry said he would continue to push the Pentagon to answer specific questions the committee posed nearly a year ago on the effects lifting this ban would have on military readiness.  

Thornberry also suggested that Congress could directly weigh in on the policy change by exploring “legislative options to address the readiness issues associated with this new policy.”  

Sen. James Inhofe, R-Okla., called on the Armed Services Committee to hold hearings, saying the change should be placed on hold until lawmakers can address the impact on military readiness.  

Adam Smith of Washington, the top Democrat on the House panel, disputed any assertion that lifting the ban on transgender service would hurt readiness, citing similar policies already adopted by U.S. allies, such as Israel, Australia, Canada and the United Kingdom.  

“By providing clarity for the service branches and removing an obsolete policy that has made it more difficult for our men and women in uniform to do their jobs, this policy will strengthen, not reduce, the military’s ability to defend the United States,” Smith said.