FDR was in his third term when the Japs attacked Pearl Harbor. He had defeated Wendell Wilkie (R) in 1940, after the electorate sort of agonized over whether to go against Washington's example of serving only two terms.
In 1944 he defeated Thomas E Dewey, Republican. Roosevelt then died in 1945, succeeded by the man from the Kansas City Pendergrast machine, Harry S Truman.
Truman won on his own in 1948, defeating (taranta ra!), Thomas E Dewey.
Harry Truman, in turn, got us into the US led United Nations "police action" in Korea in his second term.
I wonder if this writer ever studied American history. The whole issue is much more complicated than he wants to make it. His premise is very, very faulty.