Alternate Groβ Deutschland:
Starting in 1938:
History is before as in OTL. Deutschland annexes both Sudetenland and Austria as historically, but also makes a secret temporary alliance with the USSR, including the dividing of Poland, which was never wanted by both signing partners. Part of the deal is that both sign up to start the conquest of Poland in September 1939.
When September 1939 continues, the slow and less flexible Red Army, who had already started preparations to conquer East Poland in 1938, launches its attack on the Polish border on the 21st of the month, while the German Wehrmacht still stalls in Germany itself, mimicking the preparations of attack against Poland. Since the USSR also invades Finland and the Baltic States, the West, namely the UK and France deliver the USSR an ultimatum to withdraw, or risk war against these two Western Allies. Germany reacts to this by unexpectedly allying itself with these Western Allies, thereby terminating its treaty with the USSR. The result is that the USSR is unable to withdraw instantly, even if it was willing to do so, resulting in the official declaration of war against the USSR by the UK, France and Deutschland.
The fighting was a one sided affair, since the Red Army still had not recovered from Stalin’s cleancing of the Officercorps in the 30’s. It also faced tough resistance from both the small but well trained Polish Army, as well as Finnish troops, showing the weaknesses of the Red Army very clearly.
On the 24th of Oktober the Wehrmacht finally invaded Poland, to “liberate” Polish people from the Russian occupation, quickly defeating the Russian army and the Polish as well as “collateral damage”, rushing forward deep into Russian territory, before winter started to fall in. Since war had come far too early for the USSR, actually preparing for a major war, at first in half 1942, the Russians were completely surprised and defeated by the first real slug out with the German Blitz. They still had not recovered from the first blows in early 1940, when the march of the Wehrmacht restarted again, conquering vast lands of the USSR, bypassing the major cities and laying waist to Russian communication and transportlines, cutting off entire armies and forced them to surrender. In April 1940, the Germans were beginning to face problems with the over 5 million prisoners of war, resulting in some nasty affairs, also being noticed by the French and British governments, who had done almost nothing so far, due to their lack of military capacity, to fight so far away.
Both Allies of Germany politely asked Hitler to stop the crimes against the Soviet people, but found no hearing ear. They were more serious about the freedom of Poland, as it already was freed of Soviet occupation. Due to the unwillingness of the Germans, arguing that the thread of the USSR was still not over, this resulted in an ultimatum to Germany on the 9th of May, followed by the withdrawal of Germany from the earlier alliance treaty. On the 10th War was declared by the Western Allies on Germany.
Germany had expected this and anticipated on the news, by a quick and sudden invasion of the Low Countries and Northern France, before the Allies realized what was happening. Since the Wehrmacht already had won the war against the USSR basically, troops and heavy equipment had been shipped to the western borders in the winter months. The continuing war against the USSR was merely a mopping up mission of left over Russian troops and armies, while the bulk of the Wehrmacht was now on the western border, well trained and experienced, to fight yet another war.
Within a month France had capitulated, the Low Countries occupied, Norway and Danemark invaded and taken, leaving only the UK alone to face both Germany and its Allies (Italy in the Med. and Japan for the future in the Asian area.) Now the major task was to get rid of the threat of the UK, as the Germans still wanted to focus more on the remaining part of (Asian) USSR, where the Red Army still had some strong reserves, as was suspected at least. (In reality this was only on paper, since the Red Army was struck by desertions on a massive scale, and revolts against the Communist Party, resulting in the capture of Stalin in Novosibirsk, followed by the exchange of him to the Germans in exchange for a hollow promise to end the conflict. Stalin was paraded in Berlin and executed for high treason in a show trial on the 13th of August 1940).
Germany now controlled most of continental Europe in the start of 1941 and there was no real danger to its safety in the East. Only the UK remained a potential threat in the West, but dared not to invade on its own, due to the German control of the beaches and the air over the continent. Although still ruling the waves, the continental system of the Reich, resulted in a growing economy in Germany, while the UK was struck by loss of clients on the continent, as trade between the UK and European homeland was obstructed.
Then on the 21st of June 1941, the masterpiece of German Diplomacy unfolded. Churchill was forced to resign, being replaced by his predecessor Chamberlain again, who was bribed by influential British industrials to make peace at all costs, to restart the economy again. This was set in motion by German agents, who wanted to get the UK into German hands, without a fight.
On the 14th of July the same year, Chamberlain ordered an Armistice and started negotiations with Germany to end the war, which both really wanted. A week later both countries signed peace and tied up economic relations, ending the war in Europe, changing focus to the Far East, where Japan was to enter the conflict as well. (Italy too signed peace, as it was forced to do so by its German Ally.)
In the early days of November 1941, Germany and the UK allied themselves again, resulting in the combined deployment of troops and ships in each others territory. Now the Wehrmacht could enter the UK to train together with their British Ally and visa versa. The UK accepted the new political situation and shift in balance of power and actually was not all that bad after all in the new world, as it remained the biggest colonial power in the world.