In OTL, Churchill advocated the idea of the Allies attacking the USSR once they defeated Nazi Germany (Operation Unthinkable). However, the plan was deemed unfeasible (understandably, due to Soviet manpower and Allied war exhaustion) and thus was not executed.
But what if Nazi Germany's offensive was curbed early on in the war, before 1941 (how this would happen is open for debate) and the Allies subsequently attacked Soviet Russia?
Is this a feasible scenario or would the Allies just settle things diplomatically? If the former, what would the outcome be: Could the Allies defeat Soviet Russia, or would the war become a meatgrinder like during Operation Barbarossa? If latter, how would TTL post-WWII world look like? Also, how would this change the Pacific theater since Japan only provokes America to war in OTL December 1941?