David Kahn’s “The Codebreakers: The Comprehensive History of Secret Communication from Ancient Times to the Internet” exhaustive and detailed opening chapter puts to rest any notion that FDR had detailed knowledge on the date and time of a Japanese attack on Pearl Harbor. They knew something was up, of course, but their possession of Japanese diplomatic and navy codes did not pinpoint when or where.
The big question is what sort of hunch might have led to our two aircraft carriers being out on maneuvers and if Halsey, Nimitz & Co., by not sharing that hunch, had no problem with a demonstration that air power could defeat any battleship fleet and put out of commission obsolete Navy policies built around battleship tactics. We had no direct knowledge of the composition, rallying point, route or destination of Yamamoto’s attack fleet. The picture was very incomplete in the weeks leading to Pearl Harbor and all we had was guess work hampered by delays in getting decoded messages to their proper channels and inattentive chain of command bottlenecks. Had Pearl Harbor not occurred, the US would have eventually entered WWII far less effectively as a divided nation much like the US today.
What the left can never admit is that fascism in Japan, Germany, Spain, Argentina, the Balkans and in pockets of aristocracy and industry in every country in the world was a reaction to communist agitation around the world. Once it is understood that communism created fascism, history begins to make sense.
I would put it a bit differently. Communism and Fascism were competing Leftist ideologies.
Leftism was on the rise all over the world, even in the United States. It took WWII and the Cold war to educate people about the limitations and evils of Leftism, both national and international.