Bret Baier spoke on “The Five” about his third presidential book, “Three Days at the Brink: FDR’s Daring Gamble to win World War II,” which is being released Tuesday.

The book details a secret meeting that President Franklin D. Roosevelt had with Russia’s Joseph Stalin and the United Kingdom’s Winston Churchill in Tehran to win World War II.

The Tehran Conference in November 1943 is where FDR, Churchill, and Stalin plotted D-Day and the Second World War’s endgame.

BRET BAIER PREVIEWS NEW BOOK ON FDR's DARING GAMBLE TO WIN WORLD WAR II, 'THREE DAYS AT THE BRINK'

“We could have lost the war… It’s largely overlooked in history,” Baier said.

“We could be speaking German on ‘The Five,’” he jokingly added.

FDR thought he had no choice but to embrace Stalin to defeat Hitler.

The Cold War begins after FDR dies and the end of World War II, Baier noted, and Stalin backs away from the alliance.

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He said his book and other dramatic points in history must be taught so that the young in America don’t forget the past.

“Civics is lost, and we need to bring it back.”