I have read and enjoyed the Gingrich/Forstchen collaborations on the Civil War.
I think they present a plausible alternative end game and an interesting take on the character of the major figures. At least that's my perspective from a lot of reading on the Civil War and from my family tradition, grounded in Rappahannock County Virginia.
My Father graduated from Rappahannock High School in "Little" Washington, Virginia, just prior to enlisting in the Army Air Corps. He was a firm believer that if Jefferson Davis had followed the advise of his Secretary of Treasury, Judah Benjamin the Confederacy might have prevailed.
That evaluation not withstanding my father climbed into a B-17 and bombed Germany, to his later chagrin.
Planes of the 486 Bomb Group
( my Dad may have been in one of these planes) However I am not impressed with the Gingrich/Forstchen selection of Pearl Harbor for their World War II collaboration. The story rambles around without much purpose and with little conclusion.
It seems odd to me, I think they probably intend(ed) to write a conclusion but either haven't yet or decided not to. In addition every historian I have read has unequivocally concluded that the United States would defeat at the Empire of Japan in an extended war.
The Japanese were well aware of the industrial potential of the United States and knew they could not survive a war a long war.
The United States was also the major supplier of oil to Japan. When the United States embargoed oil shipments to Japan some have stated that war was inevitable. That may be, but only because Japan was unwilling to back down. Others have gone further to state that the United States forced Japan in to a war. That premise seems to be based on Japanese oil reserves and not on diplomatic analysis.
A few have gone so far as to state that the United States provoked the war. These "historians" often invoke racism in their analysis. That has always puzzled me. The stated reason for the oil embargo was the Japanese invasion and outrages in Manchurian and China. The demands the United States made on Japan were all related to their conduct in China. I have never understood how the United States placing economic sanctions on Japan for killing Chinese can be seen as racist.
In my opinion the Japanese rationally assessed the United States Naval building program in 1930's and decided that unless a military strike was made soon the United States would have predominate power and military action would be useless. They refused to make the necessary political concessions, likely because that would have caused severe political disruption in Japan, possibly a coup, a mutiny or even a civil war.
After Roosevelt's election the United States built ups its military, partly in response to world events and partly as a jobs program
USS Essex CV-9
In 1938 Congress authorized the Essex, lead ship of what would be the 24 ship Essex class of Aircraft Carriers. Eight additional ships were authorized on September 9 1940. These ships alone would match the Japaneses Aircraft Carrier Fleet. Combined with the existing ships and the Hornet also then under construction the Japanese would have been significantly outnumbered by the middle of 1943. The follow on Midway Class was already being designed.
Add to that, the construction of the North Carolina Class of (2) Battleships was complete in 1940. The South Dakota class (4) was under construction and due for commissioning by mid 1942. The Iowa Class had been ordered and the keels already laid. The even more massive Montana Class was being designed.
North Carolina Class Battle Ship This does not even include the literally hundreds of other ships on order or under construction in 1941. For example there were 21 Gleaves Class destroyers completed and commissioned between 1938 and the attack on Pearl Harbor, dozens more of the remaining 41 ships of the class were under construction. Work had already started on almost 2 dozen of the follow up Fletcher Class. Ultimately 175 Fletchers were built.
Fletcher Class Destroyer Japan could not hope to match this pace of building. And most of the Japanese leaders were aware of it. The best they could hope for, short of backing down, was to strike a blow that would make the United States reconsider or temper it's opposition to Japanese policies in China.
Unfortunately that strike didn't cow the United States and prompted a national anger that lead to the total defeat of Japan. That defeat never required more than about a third of the US war effort.
I think there is a much more interesting scenario they could have investigated.
In 1940 Germany stood undefeated and arrogant at the edge of the English Channel. There were plans for an invasion. Men and machines were being gathered.
At the time (late August 1940) the RAF was near the breaking point. There were sufficient aircraft being built but pilots were being lost before they could become effective. There was serious discussion that the RAF would need to be pulled north out of the reach of the bombers.
Consider this;
The first RAF raid on Berlin took place on the night of 25 August 1940. It is widely believed that caused the Luftwaffe to switch from bombing airfields and military installations to bombing cities. After all Goering had said in 1939
"No enemy bomber can reach the Ruhr. If one reaches the Ruhr, my name is not Goering. You may call me Meyer."
In a speech delivered on September 4 Hitler promised retribution.
Hitler threatened, "...When the British Air Force drops two or three or four thousand kilograms of bombs, then we will in one night drop 150-, 230-, 300- or 400,000 kilograms. When they declare that they will increase their attacks on our cities, then we will raze their cities to the ground. We will stop the handiwork of those night air pirates, so help us God!" The first Luftwaffe raid on London was not until September 7 1940, making the premise more than plausible.
Suppose the raid on Berlin had not happened and the RAF had pulled back. The Germans may have begun to feel they had beaten the RAF, especially if the British fed misinformation to them through the XX double agent system of dis-information.
Suppose as a result of the 3 July 1940 Battle of Mers-el-Kébir, the egotistical French Navy decided to throw in with the Kreigsmarine?
When Eisenhower tried to get the French to switch sides a couple of years later French Admirals negotiated for personal position, rather than join the liberation of France, resulting in loss of a lot of French sailors and ships but few Admirals. They might have been persuaded by a deft handling and the offer of assistance to get their battered ships and egos seaworthy. With the French on board the excellent Italian Navy could not resist helping support the invasion. The Japanese might even be persuaded to help some, in exchange for British possessions in Asia.
Given that state of affairs then Hitler may have seen this as an opportunity to eliminate a threat in his rear prior to attacking his good friend Joe Stalin.
Developing the scenario further by postponing the invasion until the spring of 1941 to allow the French ships to be repaired, the Luftwaffe to bring on new aircraft with reliable drop tanks and for the further preparation of troops, ships and landing craft. We have a scenario which might be plausible.
We look back at the successful amphibious landings later in the war and see how poorly organized such an attempt have would been. But in 1940 no one had ever mounted a large scale amphibious operation. The famous Higgins boat had only recently been shown to the Marine Corps and the final version with a full width bow ramp was yet to be developed. The doctrine of amphibious warfare had not been developed and its dangers were not understood. During the attack on Wake Island in December 1941, the initial Japanese landings were fought off by a relatively small garrison of Marines. Up to the disastrous Dieppe Raid in August 1942 it was believed that surprise could allow an assault to succeed. The May 1941 Battle of Crete had not yet exposed the weaknesses of airborne assault. The war had not really started in earnest.
One thing I have seen written is that some in Germany believed that the Royal Navy may have decided not to put forth a maximum effort to oppose the invasion, preferring to take the King and Government to safety beyond reach of the Germans, probably to Canada. This is of course absurd, but the Germans may have convinced themselves.
Of course the Royal Navy would have steamed into the middle of the invasion fleet flying Nelson's message to the fleet before Trafalgar.
"England Expects That Every Man Will Do his Duty"
Nelson's famous statement that,"No captain can do very wrong if he places his ship alongside that of the enemy", would be on the mind of every captain as well as the memory of the English ships who sailed out to confront the Spanish Armada, the last time anyone dared try to invade England.
The invasion would no doubt have been a disastrous military failure but the political calculus of the time would have changed enormously. England would be weakened enormously, possibly enough that Churchill would be put out of office and peace negotiated. Another possible outcome might be that Stalin would take the drubbing as a cue to attack Hitler while he was recovering from the loss. Japanese reaction might be to attack the United States sooner or more directly. Roosevelt may have been compelled to enter the war. Maybe India would leave the British Empire.