I do not think Germany and Japan were offered "generous" peace terms. Not only were they thoroughly destroyed, they were completely dispossessed of their political systems, much of their economic capacity, and of any territorial or colonial ambitions and claims (some of which are still outstanding). They were then made dependent on the victors for their security and stripped of any autonomous means of waging war. Nor do I think the Civil War ended with the surrender of the rebel armies, but it continued through Reconstruction until finally the Federal Government no longer had the political will to address it, giving birth to the 'Solid South' and systematic segregation. Both Clausewitz and Machiavelli advised against a "generous" peace insofar that the intent of war is to strip the enemy of his will or capacity to fight, and that an enemy wounded, but not killed, will strike you again when the time is right for them to do so ("never do a slight injury to an enemy"). So the intent isn't to find "generous" peace terms, IMO, but terms aligned with the political objectives sought in the first place so that the future behavior of the defeated actor is no longer a threat. Sometimes be 'generous', sometimes be harsh.