WASHINGTON — (CNN) The Pentagon said Thursday it was ending the ban on transgender people being able to serve openly in the U.S. military.

The announcement — which removes one of the last barriers to military service by any individual — was made by Defense Secretary Ash Carter, who had been studying the issue for almost a year.

The decision comes as the military has witnessed major changes in the role of women and the inclusion of gays, lesbians and bisexual service members in recent years.

The ground work to lift the prohibition began last year when Carter said he would study the “readiness implications of welcoming transgender persons to serve openly.”

“This is a topic of regular discussion here right now. I can tell you that we have made progress,” Pentagon spokesman Peter Cook had said last week.

The move comes after gays, lesbians and bisexuals were allowed to serve openly in 2011 when the “don’t ask, don’t tell” policy was ended. In 2015, the Family Medical Leave Act was extended to cover all legally married same-sex couples and the Defense Department amended its equal opportunity program “to protect service members against discrimination because of sexual orientation.”

Rep. Mac Thornberry, Republican chairman of the House Armed Services Committee, said Friday he had a number of longstanding questions for the Pentagon that remained unanswered.

“In particular, there are readiness challenges that first must be addressed, such as the extent to which such individuals would be medically non-deployable,” Thornberry said in a statement.

“Almost a year has passed with no answer to our questions from Secretary Carter. Our top priority must be warfighting effectiveness and individual readiness is an essential part of that.”

The Pentagon’s decision coincides with broader acceptance of transgendered individuals in the U.S., but also criticism from social conservatives.