The OP has posed a good question. I’ll start off by saying that I’m willing to take shameless advantage of data the Germans didn’t have, and of 20/20 hindsight. With that data, that hindsight, and plenty of time to think about all this, I’ve come up with what I feel is a decent plan.
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Pull back on the Eastern front to shorten supply lines. Yes, this represents the surrender of valuable, hard-fought ground. But pulling back will allow me to better feed and reammunition my troops; and will also make it easier to provide them with winter clothing. I’m surrendering some of the strategic initiative on the Eastern front, but I’m keeping the core of my army strength intact.
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Transfer some strength to the border with Turkey.
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Meet with Turkish leaders and congratulate them on the fact that Turkey will be joining the Axis. When they point out that they have not, in fact, agreed to join the Axis, my rebuttal is, “Turkey will be joining the Axis whether you guys agree or not!” That’s the stick. The carrot is the opportunity for them to reclaim much of the territory Britain took from the Ottoman Empire at the end of WWI. Hopefully this carrot and stick approach will be enough to get Turkey to join.
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Become more aggressive at seizing food supplies in conquered Polish, French, and Soviet territory. Some of the later steps will require ready access to food, and Germany’s wartime food situation was abysmal. Seizing food from conquered territory was their only real option for freeing up large quantities of additional food.
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Inform the people in conquered territories that if a young man volunteers for service in the German military, his family will receive a substantial food bonus. A bonus which might make the difference between life and death. This will allow me to add large numbers of French, Polish, and Soviet soldiers to my army.
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If a division described in 5) fights well in a particular battle, the food bonus is increased by 20%. If it fights poorly, the bonus is decreased by 20%. If a soldier is killed in combat, his family receives the bonus + 40% for the rest of the war.
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Using Turkey as my base, I would want to strike north into the Caucasus, east toward Iraq and Persia, and southwest toward Egypt. Turkish soldiers would be part of these offenses, as would any other Muslims I could convince to fight for me. I’d be willing to make substantial promises to encourage as many Muslim men to join my army as possible.
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In 1942, my approach toward the Soviet Union would be opportunistic. If there was a chance to launch an offensive the Soviets didn’t expect, and achieve a highly favorable exchange rate, I’d do it. But other than offensives like those, my default posture would be defensive.
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I would not undertake a V1 or V2 campaign against Britain. However, I would tell Werner von Braun to develop longer ranged, more advanced Aggregate Series rockets as quickly as possible.
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I would also proceed full bore with chemical weapons research and manufacture. Germany was at least ten years ahead of the Allies in the development of new chemical weapons. If a nation used a nuclear device to destroy one of my cities, I would use chemical weapons to destroy two of his. These chemical weapons would be delivered to their targets via the Aggregate Series rockets described in 9).
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I would also allocate large numbers of engineers to jet aircraft development, E-Series tanks, long range Panzerfaust weapons, assault rifles, and Type XXI U-boats.
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By 1943, I should be strong enough to launch a limited offensive in the Caucasus. The hope would be for the prong from Turkey to join the prong from the main German Army. However, all the newly trained Polish, French, Soviet, and Muslim soldiers I’ve added to my army will be largely balanced out by the huge numbers of new recruits added to the Red Army. So I won’t be able to crush the Soviet Union just yet.
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In 1945, at least 40% of my military production should be converted to Wunderwaffen; assuming there’s a relevant Wunderwaffen for the category in question. For example, at least 40% of my sub production for that year should be Type XXI U-boats, 40% of my handheld anti-infantry weapons should be assault rifles, 40% of my tank production should be E-Series tanks, and 40% of my aircraft production should be jets. I’d want that percentage to increase to at least 70% by 1946.
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By 1947 it would at last be time to launch a major offensive against the Soviet Union. My force ought to be numerically superior to the Soviets’ due to all the non-Germans I’ve added. The German component of my army will be equipped with significantly better weapons than their Soviet counterparts. Germany will have air supremacy over the battlefield due to all its jets. Access to oil from the Persian Gulf and the Caucasus will solve many of my supply problems. Instead of using rail + horse (as oil-poor Germany was often forced to do) I can use large numbers of military trucks to deliver supplies to the front.
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Hopefully I take control before Germany has declared war on the U.S. Even with the U.S. technically neutral, I still have to worry about America’s vast production capacity being used to destroy me. But at least its nominal neutrality gets me out of having to face the U.S. Army. On the other hand, pro-war forces inside the U.S. would probably succeed in getting America to go to war eventually; just as they succeeded in getting us into WWI. But even a delay of a year or two would be highly useful for my purposes.
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If the U.S. did go to war, I’d have to counter the American offensive in three ways. First, I’d use a substantial part of my German and non-German forces to deal with the American threat. Second, I’d use large numbers of jet aircraft to challenge America’s dominance over the skies. Third, I’d use smart bombs, such as the Fritz X, to attack American shipping. The more American troop ships and supply ships I sink, the harder it will be for the U.S. to sustain a European offensive. And the easier it will be for me to push them back into the sea.
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Type XXI U-boats would prove devastating against Allied shipping. This would be my defense against American arms shipments to the Soviet Union and Britain. These U-boats would also interfere with food shipments to Britain; thereby potentially forcing the British to abandon their demand for unconditional German surrender.
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With the Soviet Union defeated, and Britain forced to negotiate an end to hostilities, the time would come to convince America to give up its own demand for unconditional surrender. This would be difficult. After having neutralized hostile elements in Europe, Asia, and Africa, I’d need to build a substantial fleet. With a sufficient number of u-boats, aircraft carriers, jets, destroyers, and other ships, I could achieve dominance in the Atlantic; and begin blockading American ports. Shelling American ports. Conquering useful-looking islands in the Caribbean to use as bases for future operations. With sufficiently long-ranged bombers, such as the Horten H.XVIII, I could begin a campaign of strategic bombing against most American military production centers. Hopefully by this point American politicians would see reason, and accept the fact that America could not convince Germany to surrender unconditionally in this war any more than it could have convinced Britain to unconditionally surrender in the War of 1812.