Was there ever a serious prospect of a permanent partition of Germany in 1918 or 1945? That is, an actual attempt to disassemble "Germany" as a political entity, as opposed to the weird "two Germanies" situation that actually emerged out of WW2.
It seems a bit surprising to me that there wasn't an attempt to break up what was still a relatively novel entity, despite Germany and specifically Prussia being assigned so much of blame for the war by the Allies in both 1918 and 1945. It's not as if any principles of national self-determination were being too thoroughly upheld in either case, because Austria was specifically kept separate- not to mention Saarland, East Prussia, etc. And it's not as the Allies were over-concerned with continuity for continuity's sake, given that they went to the bother of legally obliterating Prussia.
So, was this ever actually on the cards?
In 1919, Germany was in the middle of a revolution and many observers considered the Soviet regime to be an existential threat to it, if not to Europe as a whole. It was hard enough for the French to push through the 100,000-man limit on the new Germany's military under the circumstances. An Italianized Germany would have been totally incapable of defending itself and would not have met minimum American and British security requirements.
Even relatively minor gestures toward separatism fizzled out. Tardieu and Clemenceau's somewhat halfhearted attempt to annex the Rhineland, or at least detach it from Germany as an independent republic, met with such opposition from the Anglo-Americans that it's hard to imagine the likes of something important like Bavaria getting to be independent.
The Germans, too, were unlikely to participate in particularist governments. The only thing vaguely like separatism that happened in Germany was the brief Bavarian Soviet Republic, which wasn't really a "Bavarian" thing so much as an admittance that Bavaria was the only place where the Communist Party had been able to take control of anything for any amount of time. The other problem was that the most obvious locus of separatist sentiment would have been the actual principalities, but those had just been destroyed in the course of the revolution. Of course, somebody could always have tried to create some new source of regional identity, but in practice that didn't really happen. Particularism was, ironically, associated with the failed
Kaiserreich and was therefore at least partially discredited. There was always regional culture, of course - it was, after all,
Germany - but not to the point of separatism.
So in 1919 at least, Germany wasn't broken up because nobody seemed that interested in doing so - not even the French - and the Germans weren't about to do it of their own volition.
1945's solution was more of a punt, an admittance that the United Nations had no idea what to do about Germany. They might have tried to break it up (although again I don't think it was particularly likely) but the exigencies of the Cold War intervened.