US President Donald Trump and Defence Secretary Pete Hegseth will on Tuesday address American military top brass in person, for an unusual event at a base near Washington DC.

Hundreds of military leaders, including generals and admirals stationed around the world, are expected to attend. It represents a rare gathering of so many senior personnel in one place.

No official reason was publicly provided when the leaders were summoned at short notice last week, prompting a flurry of speculation. Vice-President JD Vance has sought to downplay the event.

Security is extremely tight for the summit, which will take place at Marine Corps Base Quantico, a sprawling 55,000-acre facility in Virginia.

Behind the stage on which Hegseth and Trump were expected to speak was a large American flag, with banners showing the words "strength, service, America" and the various flags of the armed services on either side.

Confirming his own attendance on Sunday, Trump said it would be "really just a very nice meeting talking about how well we're doing militarily, talking about being in great shape, talking about a lot of good, positive things".

The president told NBC News it would be an exercise in generating some "esprit de corps" - suggesting that he saw an opportunity to galvanise his troops.

In his earlier comments, Vance had accused the media of turning it into a "big story", stressing that it was "not particularly unusual" for Hegseth's generals to meet him in person.

Some observers disagreed. Giuseppe Cavo Dragone, an Italian admiral who serves as the chair of the Nato Military Committee, was quoted by the AP news agency as saying: "As far as my 49 years of service, I've never seen that before."

Mark Cancian of the Center for Strategic and International Studies think tank told Reuters: "It is mystifying why this was not done virtually so that senior officers don't have to spend a lot of time travelling."

Mr Cancian went on to speculate that Hegseth felt his points would have more force if they were made in person.

During his tenure as defence secretary, Hegseth has made much of the need to instil a "warrior ethos" in American troops, and championed a rebrand for his government division from the Department of Defense to the Department of War.

The exact number of expected attendees on Tuesday is unclear, but reportedly could total over 800, including officers drawn from military installations as far as Europe, South Korea and the Middle East.

Many of the officers arrived hours before the event, and were seated in the auditorium according to their branch of service - Army, Marine Corps, Navy, Air Force and Space Force, easily distinguishable by uniforms.

Many of them wore campaign medals showing they had served in Afghanistan, Iraq or the American wider war on terror that was launched following the September 11 attacks in 2001.

As well as the generals, the audience comprised the senior-most enlisted officers from various US units around the world - meaning the individuals who serve as a commanding officer's main personnel adviser for their respective units.