There was a number of Allied plans for derailing the Axis, staring with 1938:
- Allow Germany and Italy to expand at the expense of minor states (i.e. Africa, Czechoslovakia, Ethiopia) and steer them into a massive war with the Soviet Union, after which the Allies could beat the survivors. Foreseeing this, Stalin dropped the Allies and aligned with Hitler.
- After Hitler had the stupidity of attacking Stalin nonetheless, a plan that mostly worked was to send aid to the USSR and let them do the heavy lifting, especially after it became apparent they wouldn't crumble in two weeks. The plan remained status quo after Pearl Harbor because the US were not yet in shape to project power into Europe.
- The Allied Strategic Bombing campaign that followed took a massive toll on Germany, and was arguably worse than a nuclear bombing would have been.
- As the Soviets began to push against Germany, Winston Churchill began to champion for an invasion of Europe that would cut the Soviets off, since he correctly foresaw that Stalin would be installing puppet regimes everywhere his troops reached. However, neither Italy nor Greece were suitable avenues of advance.
- The final plan was to land forces in France, and hope that Stalin would keep his word and not install puppet regimes (he didn't). This deal was brokered between Stalin and Roosevelt, much to Churchill's outrage, and in exchange Stalin promised to attack Japan. In the end the Western Front served as a minor diversion, distracting 10-20% of German forces from the meat grinder in the East.
- An appendix to the above would be Operation: Unthinkable, Churchill's plan to re-arm Nazi Germany and go to war with the USSR in late 1945.