Fred Trump chose the strict boarding school in Cornwall-on-Hudson mainly to straighten out his unruly son, then 13. But classmates of the future president said that while there, he got a firsthand taste of the terrors of the atomic age. In 1962, during Mr. Trump’s junior year, the United States and the Soviet Union almost went to war after the Soviet leader, Nikita S. Khrushchev, shipped missiles to Cuba to be pointed at American territory.
Mr. Trump and his classmates listened to the radio as President John F. Kennedy warned Khrushchev of American action if he did not pull back. At a time when students were used to air raid drills, the fears of these cadets went beyond the general dread of a nuclear exchange.
“Here we were, 60 miles outside of New York City, with rifles,” said Peter Ticktin, a lawyer in Florida, who was in his class. “We figured if the United States was attacked, we would have to keep order.”
For the cadets at the academy, the Korean War was less of a focus than the germinating conflict in Vietnam, where some would later serve and others, like Mr. Trump, would avoid through draft deferments — in his case because of his education and bone spurs in his feet.
But Mr. Trump was steeped in the heroics of a Korean War commander, Gen. Douglas MacArthur. The brilliant tactician who led the amphibious assault at Inchon in 1950, MacArthur later clashed with Harry S. Truman, who fired him for insubordination. At Mr. Trump’s school, however, he remained a hero: When he died in 1964, the class organized a tribute.
“We sort of disregarded the controversy around MacArthur,” said George White, another classmate. “We just regarded him as a great commander.”
As a candidate, Mr. Trump regularly invoked MacArthur’s name, often to mock his opponents for their weakness. He once said of Hillary Clinton that she “tells you how to fight ISIS on her website. I don’t think Gen. Douglas MacArthur would like that too much.” Aides said the president has continued to talk about his exploits in the White House.