Hundreds of American generals and admirals from around the world will begin arriving in the national capital area over the next three days for what is now being described as a chance for the secretary of defense, Pete Hegseth, to lay out his vision for an enhanced “warrior ethos” in the military.

In background briefings with multiple news organizations late this week, White House and Pentagon officials have put to rest speculation that the Tuesday meeting, whose purpose has not been officially disclosed, would involve widespread dismissals and demotions of senior commanders or serve some other mysterious purpose.

Rather, it appears intended to provide Mr. Hegseth, an image-conscious former TV news anchor, an opportunity to speak directly to the nation’s top commanders about the way he expects the military to comport itself in future. Several sources said the encounter will be recorded on camera for future public distribution.

While dismissing much of the anxiety about the meeting, several of the sources acknowledged concerns about the logistical and security complications, as well as the cost, of pulling an estimated 400 top-ranking officers away from their posts, sometimes from conflict zones halfway around the world. Exacerbating the concern, the meeting is scheduled on the eve of a possible government shutdown.

The meeting, to be held at a Marine base 35 miles south of Washington, D.C., and described by one source as a “pep rally,” is “meant to be a show of force of what the new military now looks like under the president,” a White House official told CNN.

“It’s about getting the horses into the stable and whipping them into shape,” another defense official told the network, which said Mr. Hegseth is expected to discuss new readiness, fitness and grooming standards for the military.

“And the guys with the stars on their shoulders make for a better audience from an optics standpoint. This is a showcase for Hegseth to tell them: get on board, or potentially have your career shortened.”

President Trump, who is not expected to participate in the meeting and reportedly was not involved in the planning, has suggested in Oval Office comments this week that many of the officers are excited to be coming.

“It’s great when generals and top people want to come to the United States to be with a now-called secretary of War,” Mr. Trump said during a signing of executive orders on Thursday.

He noted that America is selling military equipment “to others, other countries, and a lot of generals want to be here,” he said. “And they want to look at the — they’re also going to be touring equipment sites. They’re going to be talking about the newest weapons, etc.”

The call to Virginia went out only this week according to the Washington Post, which first reported the meeting, leaving the officers little time to schedule travel and arrange for a continuity of operations, often in highly sensitive areas such as the Middle East and East Asia.

The Post said the order applies to all senior officers with the rank of brigadier general or above, or their Navy equivalent, serving in command positions, along with their top enlisted advisers.

ABC News cited Pentagon statistics from June showing 838 total general officers and admirals on active duty but said it is difficult to determine how many of them are in command positions versus staff positions. Other reports have suggested about 400 officers will be at the meeting along with one top adviser apiece.

The lack of any public explanation of the purpose of the meeting prompted initial speculation that it might be related to Mr. Hegseth’s stated intention to reduce the number of top officers across the services.

In a May 5 memo reported by CNN, the secretary ordered a 20 percent cut in the number of four-star generals and admirals and a 10 percent cut in the total number of general and flag officers across all branches. The memo described the move as “critical” to streamlining leadership and eliminating redundant command structures.

Also this year, Mr. Hegseth removed 15 senior officers from their posts, including General Charles “CQ” Brown, Jr. the then-chairman of the Joint Chiefs of Staff, and Admiral Lisa Franchetti, the Navy’s top admiral.