John McCain's almost six years as a prisoner of war (POW) do not make him a war hero in Donald Trump's eyes, but the tycoon turned presidential hopeful says he himself "always felt that I was in the military" because of his military boarding school experience, Politico reported.

Trump, who obtained a draft deferment during the Vietnam War and never served in the armed forces, suggested that his five years at the New York Military Academy provided him with "more training militarily than a lot of the guys that go into the military."

The statement is part of an upcoming biography titled "Never Enough: Donald Trump and the Pursuit of Success," excerpts of which were published this week by The New York Times.

"After the Vietnam War, all those military academies lost ground because people really disrespected the military," the former "Apprentice" star alleges in the book penned by Michael D'Antonio. "They weren't sending their kids to military school. It was a whole different thing, but in those days -- 1964 I graduated -- that was a very good thing or tough thing, and it was a real way of life at military academy."

In July, Trump made headlines by challenging the Arizona senator and former Navy pilot, McCain, who in 1967 was shot down by a missile over Hanoi and was brutally tortured by his Vietnamese captors when he refused to sign "confessions" and other propaganda statements.

"He was a war hero because he was captured," Trump noted about McCain at a campaign event, according to Politico. "I like people who weren't captured."

In response, the Silver Star recipient told USA Today that Trump did not owe him an apology personally, but that the GOP front-runner should not have denigrated the memory of others who fell into enemy hands in Vietnam and other conflicts.

D'Antonio, meanwhile, noted in his book that not many New York Military Academy alumni would compare military school with actual service in the armed forces.

"But the assertion was consistent with the self-image Trump often expressed," the author wrote.