Tom Vanden Brook

USA TODAY

WASHINGTON — The architect of controversial Pentagon personnel policies, including the proposed acceptance of transgender troops, will leave his post in April, the Pentagon announced late Monday.

Brad Carson, the Pentagon's top civilian for personnel policies, had pushed forward a string of initiatives that include opening combat jobs to women and expanded maternity leave.

"Brad Carson has developed some of the most important and groundbreaking work in years to modernize our personnel policies," Defense Secretary Ash Carter said in a statement. "At my direction, he charted a path forward for the Department and our people that will leave a lasting legacy, and will improve the mission effectiveness, readiness and the quality of life for our civilian workforce, uniformed service members and families.

Carson had a rocky confirmation hearing last month before the Senate Armed Services Committee. He had been named to fill the spot as undersecretary for personnel on an acting basis. But a federal court determined that in performing the job before confirmation, he had violated federal law, namely the Vacancies Act.

In a statement, Carson said the Senate's concerns about the Vacancies Act and the implementation of several key policies prompted his decision to step down. He plans to leave office in April.

"I believe it is a perfect time to move on," Carson said.

Carson took the job in 2015 and moved quickly to change policies affecting more than 1 million troops. Opening the ranks to transgender troops has been one of the most controversial moves. The policy, not yet enacted, would allow transgender troops to serve and seek medical treatment and counseling. Identifying as transgender now is grounds for dismissal, although a de facto moratorium has been in place.

Carson was also author of Carter's Force of the Future initiative. It established a number of programs designed to attract and retain talented, young troops. The plan boosted maternity leave to 12 weeks, provided lactation rooms for nursing mothers on military bases and increased opportunities for troops to serve internships with industry and take breaks to raise families without damaging prospects for promotion.

Carson, in his statement, praised the work of his top lieutenant, Morgan Plummer, an Army combat veteran. A Navy veteran himself, Carson saluted Carter for his willingness to push for changes to personnel policy.

"There are people who say that the Pentagon can never reform itself," Carson said. "I believe Dr. Carter and our team have shown that it can."

Carson's efforts on gender equality, particularly opening combat roles to women, will likely be seen as the most significant changes, said Todd Harrison, a military budget expert at the Center for Strategic and International Studies. But senior military officials chafed at other fundamental reforms such as altering the promotion system, Harrison said.

"Carson is one of the good guys who came in to the position really trying to make some lasting change for the better," Harrison said. "He had been given a mandate by Secretary Carter to be bold and move fast and he did. The problem is that the bureaucrats are entrenched and do not respond well to bold and fast."

At his Senate confirmation hearing in February, Armed Services Committee Chairman John McCain, R-Ariz., blasted Carson and the Force of the Future initiative as "an outrageous waste of official time and resources" during a time of tight budgets.

The price tag for freezing the sperm and eggs of troops is estimated at $150 million over five years.

Carson joined the Obama administration in 2011 as the Army's top lawyer. He moved on to become Undersecretary of the Army before taking on the top personnel post in April 2015. Carson, a Democrat, also served as a congressman from Oklahoma.