I'll just repost (and adapt) and collate a couple of posts of mine from
this thread:
The topic of there being different occupation zones comes up from time to time. However the history of the zones requires that a POD occurs in 1943, rather than 1944. I did a
map series on this in the New OTL Maps thread which
was inspired by
@Stateless ' own
maps and
source, plus
further research (to anyone interested, scroll down to p. 131 and read onwards from there).
The problem with a 1944 POD (Horthy defecting to the Allies more successfully in this case) that then relies on the February 1945 Yalta conference is that the basic outline for the zones had been agreed as far back as
1943 and in February 1944 (that is
before the Normandy landings) the remaining areas of disagreement concerning the zones was not between the Western Allies and the Soviets, but between the British and Soviets on one hand and the Americans on the other - the British and the Soviets came up with practically identical proposals for the zones in February 1944 (if not from 1943), but it was FDR who held out for very different boundaries which were also unrealistic in that it would require the Americans to occupy northern and northwestern Germany (which FDR in particular and some other Americans wanted because they envisioned occupying Germany for only 1-2 years and didn't want to rely on supply lines through France but rather via the sea; additionally they envisioned the need to withdraw troops from Europe to continue pursuing the war against Japan which was not
expected to be finished until 1946 at the time*) while the British occupied southern Germany (and the Soviets occupying the east). This was unrealistic for two reasons; first because Operation Overlord had the Americans landing on the westernmost beaches in Normandy while the British landed on the eastern beaches. Thus when the Americans and British pushed south into France and then turned east into the Germany, the Americans would end up, solely on the basis of geography, in southern Germany, while the British would end up in northwestern Germany (this was thus the basis of the British proposal for the zones in 1943-1944). To get FDR's preferred arrangement of the Americans in northwestern Germany and the British in southern Germany would require changes in the deployment plans for Overlord
OR it would require that the two vast armies switch places at some point during the advance into Germany, or after VE Day (which would be a very large and largely unnecessary logistical undertaking). Secondly it was unrealistic because it did not use existing administrative boundaries as the basis for the zones (which is what the British and Soviet proposals did - though they were so close in outline apparently they should probably be considered as one proposal). This would cause major headaches administratively as rather than appropriate existing administrative machinery, the Allied military governments would now have to create whole new apparatuses which would likely cut across existing administrative borders and cause confusion and inefficiency (if one thinks about it, the division of Austria into zones also followed existing administrative divisions and it was clearly for similar reasons). For this reason a zonal boundary on the Weser would also be a headache as it would cut across longstanding administrative boundaries that the Allies simply could have co-opted for their own purposes. It would have the same problem as FDR's proposals.
If I'm not mistaken the basic zonal boundaries were agreed in outline in January 1944 (before Hungary got occupied by Germany), then more concretely by May 1, 1944 (again this is before the Normandy landings) when the Americans agreed with the Soviet and British proposals on the boundaries of the eastern zone allocated to the USSR and then ultimately in the
London Protocol and in the Second Quebec Conference of September 1944 and the only thing left to determine was which Ally (America or Britain) was going to occupy the northwestern zone and which ally (Britain or America) was going to occupy the southern zone. Actually, by the time of Yalta, the disagreement wasn't over the zonal boundaries, or even over which zones were going to be occupied by the British and which one by the Americans (that had been agreed on September 16, 1944 when the British finally convinced FDR that it would be better for the British to take the northwestern zone, while the Americans took the southern zone) but over whether the Americans would have administrative control over the districts of Bremen and Bremerhaven (as the Americans expected) rather than just control over the port facilities in those towns (as the British expected). The solution to that minor dispute came just before Yalta when the Americans agreed to keep conform their occupation policies in the Bremen/Bremerhaven enclave with those of the surrounding British zone, if the British relinquished full control over that enclave to the Americans. The only other thing that was then agreed by the time of Yalta was that France would get an occupation zone carved out of the British and the American zones (hence why France's occupation zone ended up looking the way it did).
*since the British had put forward a planned invasion of the Home Islands for 1947-
1948 which the Joint Chiefs of Staff would mean prosecuting the war for far too long and in the First Quebec Conference of August 1943 it was agreed to Japan should be forced to surrender within 1 year of Germany's surrender.
So if persons can come up with an 1943 POD concerning the zones, that would be interesting, but it would likely require that:
1. the Normandy deployments are different - how that affects the campaign in France (if at all) would need to be considered. In particular it would require the western Allies to have logistical plans in place to expect and support advances faster than expected (which in turn will also be dictated by consideration for the war against Japan). In OTL the advances being faster than expected
threw up some logistical problems
2. FDR gets his way against the British and the Soviets who in this instance actually have the same idea on how Germany should be split into occupation zones
3. For a Soviet zone up to the Weser, a much better Soviet performance from 1941-1942 such that the Germans never penetrate the USSR as far as they did in OTL and are able to push the Germans back through Central and Eastern Europe into 1942 and are closing in on Berlin from 1943. This however, might render the Normandy landings pointless as the war might be over before the Americans and British need to land in France (well to land in France
opposed anyway rather than simply landing to effect the evacuation of German troops from France in unopposed landings).
and this in turn would likely render the conflict from 1943 onwards unrecognizable to us from OTL because of the vast butterflies likely to be unleashed (not least, if Berlin falls in 1944, then the Soviets don't suffer the losses they did in OTL which allows them to have more forces available in the campaign against Japan, in OTL in
June 1945 the Soviet leadership discussed what would be required to capture Hokkaido and Zhukov suggested four divisions were needed)