1, The USA with its massive resources and industrial potential has to stay out of the war. For this to happen, you pretty much have to build in an assumption that FDR is out of the picture and a very different Administration is calling the shots.
2. It helps a great deal if there is no Dunkirk evacuation.
3, Conflict with the USSR seems to be pretty much unavoidable and success depends on taking Moscow in 1941 - and probably also controlling the Black Sea to facilitate a follow on seizure of the Caucasus in 1942. It helps a great deal to get Turkey into the war on the Axis side and the most likely scenario would be a blundering offensive by the Soviets into northeastern Turkey in 1939 (like the Finland offensive) aimed at reconquering the territories lost to Turkey at the end of WWI.
4. Then it helps to get a head start on Barbarossa in 1941 by getting lucky with Spring weather and having no detour down into the Balkans (if there is no Dunkirk evacuation, this may be more plausible).
5. A key factor would be for the Nazis to become Notzis and abandon extreme racism by dialing down antisemitism and courting the minority nationalities of the USSR.
6.. Then if Japan attacks the USSR rather than the USA, it keeps the USA out of the war at least for a while and creates yet another burden for the USSR in addition to Finland and Turkey.
7. Of course, it would help to have the benefit of a mild winter in 41-42.
Even with all of this, the USSR is not really knocked out but it may be reduced enough so that the regime gets shaky or the remainder of the USSR is a much less formidable opponent.
Looking at this, it is hard to imagine what they were thinking when the started the war. The logistics are so overwhelming and the imbalance in industrial production so great that one wonders whether an insanity defense should have been attempted by the lawyers representing the Nuremberg defendants.
2. It helps a great deal if there is no Dunkirk evacuation.
3, Conflict with the USSR seems to be pretty much unavoidable and success depends on taking Moscow in 1941 - and probably also controlling the Black Sea to facilitate a follow on seizure of the Caucasus in 1942. It helps a great deal to get Turkey into the war on the Axis side and the most likely scenario would be a blundering offensive by the Soviets into northeastern Turkey in 1939 (like the Finland offensive) aimed at reconquering the territories lost to Turkey at the end of WWI.
4. Then it helps to get a head start on Barbarossa in 1941 by getting lucky with Spring weather and having no detour down into the Balkans (if there is no Dunkirk evacuation, this may be more plausible).
5. A key factor would be for the Nazis to become Notzis and abandon extreme racism by dialing down antisemitism and courting the minority nationalities of the USSR.
6.. Then if Japan attacks the USSR rather than the USA, it keeps the USA out of the war at least for a while and creates yet another burden for the USSR in addition to Finland and Turkey.
7. Of course, it would help to have the benefit of a mild winter in 41-42.
Even with all of this, the USSR is not really knocked out but it may be reduced enough so that the regime gets shaky or the remainder of the USSR is a much less formidable opponent.
Looking at this, it is hard to imagine what they were thinking when the started the war. The logistics are so overwhelming and the imbalance in industrial production so great that one wonders whether an insanity defense should have been attempted by the lawyers representing the Nuremberg defendants.