The United States Army no longer has a Senate-confirmed chief as a Republican senator continues to obstruct military nominees, a move military leaders said on Friday jeopardizes readiness and weakens officer retention.

As retiring Army Chief of Staff General James McConville relinquishes command, the United States military will be without a confirmed leader for the first time in history, according to the Pentagon.

“In our dangerous world of security, the United States demands orderly and prompt transitions of our confirmed military leaders,” U.S. Defense Secretary Lloyd Austin said during the change of command hearing. “Great teams need great leaders.”