Marine Corps without confirmed commandant for 1st time since 1910 after GOP senator's blockade

Gen. David Berger stepped down as commandant of the Marine Corps on Monday, but had no permanent successor to hand off to, leaving the service without a Senate-confirmed leader for the first time since 1910.

The lapse in command is because Republican Sen. Tommy Tuberville of Alabama is blocking senior military nominations in protest of a Pentagon abortion policy.

"I know that everyone here is looking forward to the rapid confirmation of a distinguished successor to Gen. Berger," Defense Secretary Lloyd Austin said during what was called a "relinquishment of command" instead of a "change of command" ceremony. "It's been more than a century since the U.S. Marine Corps has operated without a Senate-confirmed commandant."

For now, President Joe Biden's pick to be the Marines' new service chief, Gen. Eric Smith, will step in as acting commandant. Smith will have to balance his new responsibilities with those of his current role as assistant commandant until he is confirmed.

Speaking after Austin at the Marine Barracks, Washington, D.C., Berger implored the Senate to confirm his successor, but did not appeal to Tuberville by name.

"I'm with you, Mr. Secretary. We need the Senate to do their job so that we can have a sitting commandant that's appointed and confirmed. We need that house to be occupied," he said, gesturing to the commandant's residence.

In December 2022, Tuberville pledged to block all senior military and civilian Department of Defense nominations over a new Pentagon policy that covers the travel costs of service members seeking abortions in states outside of where they are stationed if they are based in a state that bans the procedure.

Before the policy was implemented, Tuberville concluded a letter to Austin saying, "it is my conviction that this proposed policy change is illegal, circumvents Congress, and exceeds your authority."

"Hundreds of well-qualified military leaders are now being held up by Sen. Tuberville," Pentagon deputy press secretary Sabrina Singh told reporters Monday.

As of Friday, more than 250 nominations have been blocked, according to Singh.

Tuberville's efforts could also slow the nomination of America's next top military officer.

Air Force Gen. CQ Brown, Biden's pick to replace Gen. Mark Milley as chairman of the Joint Chiefs of Staff, will face Tuberville and the other members of the Senate Armed Services Committee at a confirmation hearing Tuesday. If Tuberville doesn't relent or if no workaround is exercised by the time Milley retires at the end of September, the vice chairman of the Joint Chiefs of Staff will step up in an acting capacity.

As a result of the delays, the DOD is asking some officers to delay retirement, and asking others to assume more senior duties without being promoted, meaning they will not see a corresponding pay increase until confirmed by the Senate, according to Singh.

Tuberville's tactic has been met with criticism not just from the Biden administration and Senate Democrats, but members of his own party. In May, Senate minority leader Mitch McConnell told reporters, "No, I do not support putting a hold on military nominations."

"The longer these unprecedented holds remain, the greater risks the department runs in experiencing knowledge and expertise gaps in certain critical and often difficult to fill positions, and the downstream effects will continue to impact the readiness of the force," Singh said. "We urge Sen. Tuberville to lift his hold, and urge the Senate to confirm these exceptional general and flag officers."

The Democratic chairman of the Senate Armed Services Committee, Jack Reed, spoke out on the Senate floor.

"Our inaction matters. More than just our generals are watching," Reed said. "These holds ripple through the ranks and, trust me, noncommissioned officers are watching. Families are on hold -- they can't move. Spouses can't take new jobs. Kids can't move to get into new schools.

"This is not a game. These are real lives that have been upended," he said.

ABC News' Trish Turner contributed to this report.