President Donald Trump's new national security adviser, Lt. Gen. H.R. McMaster, needs Senate confirmation to remain a three-star general in his new post .

His job, like virtually all those in the West Wing of the White House, doesn't need Senate approval. But his decision to remain on active duty as a three-star Army general will require Senate approval.

Under the military’s arcane system for ranking three- and four-star generals and admirals, the ranks are considered temporary and tied to the position, so when officers move jobs they have to be reconfirmed by the Senate at that rank. Federal law allows for the president to appoint generals and admirals to “positions of importance,” but also requires Senate confirmation within 60 days.

“Gen. McMaster does not require Senate confirmation to serve as national security adviser,” said a Senate Armed Services aide. “However, if it is the president’s desire that Gen. McMaster serve as national security adviser while in his current grade of lieutenant general, the law requires that Gen. McMaster would have to be reappointed by the president and reconfirmed by the Senate in that grade for his new position.”

As an alternative, McMaster could retire from active duty or take the national security adviser job as a two-star general. But the White House has already said he'll remain on active duty, and he isn't likely to accept a demotion.

Still, the confirmation process doesn’t mean McMaster is likely to face a hearing — at least if history is any guide.

The last active-duty general to serve as national security adviser was Colin Powell, in the final years of the Reagan administration.

Powell did not get a confirmation hearing, according to Arnold Punaro, who was then the Senate Armed Services Committee staff director, as three-star appointments typically do not. But Powell did spark debate on the Senate floor.

Punaro, a retired lieutenant general who is now a defense industry consultant, said an Iran-Contra select committee had recommended against an active-duty military officer as national security adviser — and then-Senate Armed Services Chairman Sam Nunn (D-Ga.) had to wrangle up support for Powell from the leaders of the select committee.

“Nunn himself had reservations,” Punaro said. “He preferred a retired person, but he felt very strongly we ought to make an exception for Colin Powell.”

In fact, in a floor speech announcing his support for Powell, who retired in 1993 as a four-star Army general after serving as Joint Chiefs chairman, Nunn said he didn't want to see a precedent set.

“I am very reluctant and will be reluctant to see this action … repeated in the future,” Nunn said.

McMaster’s nomination would be handled by Senate Armed Services Chairman John McCain (R-Ariz.), who was a key advocate of granting a congressional waiver to retired Marine Gen. Jim Mattis so he could become Defense secretary, even though he had been out of uniform only three of the required seven years.

McCain is likely to push for Senate confirmation for McMaster, too. "I could not imagine a better, more capable national security team than the one we have right now,” McCain said Monday after the president announced McMaster's White House appointment.