After the successes of D-Day and the breakout from Normandy, there was a sentiment that the Allies could end the war by Christmas. Of course, the failure of Market Garden put an end to these hopes and the war lasted until May '45. But could it have been different? With a POD no earlier than the initial D-Day landings of June 6, 1944 is it possible for the Allies to force a German surrender by Christmas '44?
Probably not.
Is avoiding Market Garden and adopting a better plan for crossing the Rhine enough?
Definitely not. I'll try to get there with the best outcomes for the Allies.
"Force a German surrender" means no successful assassination of Hitler or VALKYRIE coup, which IMO could and probably would lead to voluntary German surrender. Also no additional German unforced major blunders.
1) Mark Clark attacks to the rear of the Germans in southern Italy instead of taking Rome first.
Deleted because the PoD is before D-Day. Damn.
2) More aggressive movement against the Falaise neck. The pocket is closed and the German forces there destroyed. About 100,000 additional German losses.
3) Better executed Slovak national rebellion. (There was a stub timeline on this recently.) The Soviets break through Carpathians to link up with the Slovaks, flanking the German forces attempting a fighting retreat from Romania, Greece, and Yugoslavia. The retreat becomes a rout; Soviet forces sweep across Hungary, which successfully defects, reaching Vienna by the end of September, with 250,000(?) extra German losses.
4) Better planned MARKET-GARDEN. The attack succeeds in capturing the Arnhem bridge and 30 Corps gets across to the edge of the Zuyder Zee. I'll make an optimistic guess here: supply to the German forces in Zeeland are cut off and South Beveland and Walcheren Island fall faster than OTL; by mid-October.
5) The additional losses at Falaise and in the Balkans allow Third Army and Sixth AG to clear Alsace and Lorrain by mid-October...
But now there's only 8 weeks left. Allied supply arrangements had to be reorganized. So do Soviet arrangements. I don't see how it can get done in time for a Rhineland campaign and Rhine crossing befor mid-November.
Just too late.