President Biden will address the graduating class of cadets at the U.S. Military Academy, West Point, on Saturday, delivering a commencement speech at a moment of military upheaval abroad, university protests at home and a looming White House rematch with former President Donald J. Trump.

Mr. Biden is expected to congratulate the Army’s newest officers, describe the global challenges facing the military and remind the cadets of the oath they took — not to the president, but to the Constitution, according to a person familiar with the speech who asked for anonymity because he was not authorized to discuss it.

Aides said Mr. Biden was hoping to use the moment to draw a sharp contrast with Mr. Trump, who delivered the commencement address at West Point in 2020 and drew criticism even from some within the ranks of the academy for what they said was Mr. Trump’s desire for personal loyalty from the people around him.

Saturday morning’s speech will mark the third time that Mr. Biden has been West Point’s commencement speaker, after appearing twice as vice president. During his first three years as president, he spoke at the Coast Guard, Navy and Air Force graduations.

The president’s return to the Army’s elite educational institution will provide him with a collegiate backdrop far from the student protests over his handling of the war in Israel. Polls show deep concern about the president among young people, fueling questions about his re-election chances in the fall.

At West Point, which is an hour north of New York City, he will address about 1,000 sharply dressed cadets, each in their signature gray uniform and white gloves, in Michie Stadium.

Some presidents have used the lectern at West Point to unveil new military doctrines or announce major initiatives. In 2002, President George W. Bush used his commencement address there to make his case for a U.S. war against Iraq in the aftermath of the Sept. 11 attacks nine months earlier, telling the cadets: “We must take the battle to the enemy, disrupt his plans and confront the worst threats before they emerge.”

Aides said Mr. Biden had no plans to make major foreign policy announcements on Saturday. But his message to the graduates is likely to echo the central theme of his re-election campaign, though without any mention of Mr. Trump by name or a direct election-year appeal to the newly minted officers and their families.

Mr. Biden has argued that democracy is at stake in the upcoming presidential election, and that the basic institutions of government — including the military — are at risk if Mr. Trump is allowed to return to the Oval Office.

Mr. Trump gave his speech at West Point just months after Mark T. Esper, then the secretary of defense, and Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, joined him for a walk through Lafayette Park near the White House amid a harsh crackdown by police and the military of a Black Lives Matter protest following the death of George Floyd.

In an open letter to the West Point graduates, former members of the academy urged them to remember where their obligations lie.

“We pledge service to no monarch; no government; no political party; no tyrant,” the former West Point cadets wrote to their successors. “Your oath is to a set of principles and an ideal expressed in the Constitution and its amendments.”

Mr. Biden’s speech comes as he grapples with the fallout of two grinding wars abroad, in Ukraine and Gaza. He has pledged that he will not deploy American forces to the ground for either conflict. But both have nonetheless drawn the United States deeply into the fray, by providing weapons, diplomatic support and humanitarian relief.

And there are other looming threats: the risk of a Chinese attempt to seize Taiwan; attacks from Iran like the missile barrage against Israel that the United States help deter; and instability across parts of Africa and Central and South America.

Mr. Biden is also hoping to avoid the stumbles that have occasionally marred presidential appearances at military commencements.

During his 2020 address at West Point, Mr. Trump was seen drinking awkwardly from a glass with two hands, and later walking very slowly down a ramp. Videos of both moments went viral, raising questions among some of his critics about his health and vitality.

Last year, Mr. Biden tripped and fell while he was shaking hands with the graduates at the Air Force Academy, an incident that aides later blamed on a sandbag on the stage. The president, who was 80 at the time, was quickly helped up by several people and was “fine,” according to his aides.