Acting Defense Secretary Mark Esper is expected to soon be formally nominated to lead the Pentagon, setting off a complicated leadership replacement shuffle at the highest levels of the Pentagon and the military services.

Eric Chewning, Esper’s chief of staff, told reporters Tuesday that the Senate controls the timing of the confirmation hearing and vote. But if senators act quickly, President Donald Trump’s third defense chief could be confirmed within a week, he said.

In a statement, Senate Majority Leader Mitch McConnell said he looks forward to the Senate’s “swift consideration” of Esper’s nomination, but he did not specify any timeline. He said he met with Esper on Tuesday and called him an impressive leader with a distinguished record.

There has been no confirmed Pentagon chief since Jim Mattis resigned at the end of last year. Patrick Shanahan, who was Mattis’ deputy, served as acting secretary for about six months, but he stepped down last month before he was formally nominated for the job. Trump immediately named Esper acting secretary and indicated he would nominate him soon.

Chewning and others said Tuesday that they don’t know exactly when the nomination will go up to the Senate, but said it will be “shortly.”

The Senate has been known to act swiftly on defense nominations, particularly if they are well coordinated. Robert Gates, for example, was selected by President George W. Bush to be Pentagon chief shortly after the midterm election in 2006. His formal nomination went to the Senate Armed Services Committee on Dec. 4, the hearing was the next day and he was confirmed by the full Senate on Dec. 6.

Esper’s formal nomination will trigger a domino effect that is far more complex than usual because many of the top Pentagon and military service jobs are filled by people who are serving in an “acting” capacity.

Figuring it all out has taken department lawyers much of the last few weeks, and Chewning laid out the latest scenario.

Immediately after the White House sends Esper’s nomination to the Senate, he has to step down because by law he can’t serve in the position for which he has been nominated. He will return to his former job of Army secretary.

Based on an executive order detailing the line of succession, the deputy defense secretary would normally step up to serve as acting secretary, but there is currently no confirmed deputy. The second in line is the Army secretary, but since that would be Esper, the department has to move to the third person in line, which would be the Navy secretary, Richard Spencer.

The Navy’s undersecretary, Thomas Modly, would become acting secretary there. And in the Army, Undersecretary, Ryan McCarthy — he had stepped up to fill in as secretary of that service — will go back to his regular job.

The Navy moves add more upheaval to that service because the admiral nominated to become the next chief of naval operations said last weekend that he will instead retire, due to ethical questions.

If the Senate confirms Esper, officials expect that David Norquist would be nominated for deputy secretary. Norquist was confirmed for the job of undersecretary and comptroller in June 2017. But when Shanahan was moved up to acting secretary in January, Norquist was tapped to perform the duties of the deputy, and he continues in that job now.

Chewning said Spencer is already receiving briefings so that he will be able to step in and stay on while Esper is nominated and considered by the Senate. He said Esper is already meeting with senators on Capitol Hill and preparing for the nomination process.

(AP)