That was news to everyone, including officials at West Point, according to three people involved with or briefed on the event. The academy had been looking at the option of a delayed presidential commencement in June, but had yet to complete any plans. With Mr. Trump’s pre-emptive statement, they are now summoning 1,000 cadets scattered across the county to return to campus in New York, the state that is the center of the outbreak.

“He’s the commander in chief, that’s his call,” said Sue Fulton, a West Point graduate and former chairwoman of the academy’s Board of Visitors. “Cadets are certainly excited about the opportunity to have something like the classic graduation, standing together, flinging their hats in the air.

“But everyone is leery about bringing 1,000 cadets into the New York metropolitan area for a ceremony,” she added. “It’s definitely a risk.”