One thing that bedevilled me, as I worked on the outline for what would become Twilight of the Gods, was the question of just how far the Reich could realistically go without becoming a Nazi-Wank. This is not actually an easy question to answer. Very few people in 1939 would have believed that the French could be crushed so easily in 1940 — indeed, the Germans came alarmingly close to running out of ammunition during the Polish Campaign — and very few commenters in 1941 gave the Soviets more than six months before they too were crushed.
Post-war writers have added their own spin on matters. Books such as The Man in the High Castle and In The Presence of Mine Enemies assumed that an alternate Reich would invade and occupy America in the process of an inevitable rise to global supremacy. Others — including myself — predicted a resumption of the war between Germany and Britain (and America). But just how realistic are such scenarios?
The important point to bear in mind is that Hitler lived during what I believe to be the last great period of conquest. Hitler’s armies were armed and trained to race forward, seeking out the weak points in enemy defences and smashing through opposing armies before their enemies could react to the threat. Advances on such a scale were simply not possible during the Great War. At the same time, the threat of nuclear annihilation simply did not exist. The RAF could — and did — bomb Germany, but — even if chemical weapons had been deployed — their ability to bring Germany to its knees was practically non-existent. Defence planners believed that the bomber would always get through, yet… so what?
By the time the 1960s rolled around, the armies were far more powerful — but, at the same time, more constrained. A Russian drive westward would almost certainly have triggered a nuclear response, when — if — NATO was unable to handle it. Russia would have been devastated, along with Western Europe. It is one of the many ironies of the Cold War that the US, which had a considerable nuclear supremacy, spent most of the war believing that it was fighting to catch up.
One may assume, of course, that Hitler was mad enough to consider launching a full-scale nuclear war. It would certainly fit into a story! But, at the same time, Hitler was rather more rational than we prefer to believe. Certainly, most of his pre-1944 decisions were rational based on what he knew at the time. Marching to Stalingrad was disastrous — we are told in hindsight — but it wouldn’t have looked like a certain failure in 1943.
The other two major limitations on the Third Reich lie in their army and air force. Hitler had a fairly modern battle fleet — but it was grossly outnumbered by the British. (Adding the Italian Navy to the Reich doesn’t really tip the balance.) Hitler could — and did — threaten supply lines between Britain and her empire (and America) but he couldn’t strike directly at Britain itself. Meanwhile, the Luftwaffe was largely a short-range striking force. The Germans never had a successful long-range heavy bomber, ensuring that large parts of Britain were immune to German attack (and America was completely out of range.) Any attempt to assess the limits of the Third Reich must take those factors into account.
So… how far could Hitler have gone?
To the west, Operation Sealion was pretty much a pipe dream. Some authors have speculated that the invasion might have been possible, but the Germans really had too many limitations — a shortage of shipping, among others — to make Sealion anything other than a very risky gamble. Hitler simply could not get across the English Channel.
For this to change, Hitler would need to reshape his air and naval forces radically, following a strategy that would have no viable purpose other than the invasion of Britain. Even if the Hitler of 1938 was prepared to make the investment, long before France was crushed in 1940 and Sealion became necessary, such programs would very definitely change the political situation during the run up to the war.
[The idea that Hitler could have invaded America is so absurd not to require further discussion.]
Hitler presumably has no need to occupy either Spain or Portugal. Neither power was inclined to challenge the Third Reich overtly. However, he may well want to pressure the Spanish to take Gibraltar and the Portuguese to break ties with Britain. Both steps could be taken, at considerable economic cost to both Spain or Portugal. In such an eventuality, one might see Hitler facing his own version of the Peninsula War.
To the south, the problem facing Hitler is logistics. The Germans might have been better than the British at desert warfare, but Rommel was always operating on a shoestring. Hitler always saw the desert war as a sideshow, rather than a potential way to bring the British to heel. And again, from his point of view, he was right. Nazi gains in the Middle East would always be tenuous as long as the British remained undefeated and Soviet Russia loomed to the east.
Taking Malta during 1940 would have been easy — even the Italians could probably have done it. (Indeed, a timeline where Germany invades Malta instead of Crete might lead to German dominance in the region.) Malta would serve as a giant airbase, allowing the Germans to drive the Royal Navy out of the region and ship additional supplies to Rommel. Thus reinforced, Rommel might have been able to push forward to Suez and drive into Palestine, creating a massive humanitarian crisis. Scenting British weakness, the Arabs would rise in revolt, enthusiastically supporting the Germans. As the British position crumbled, the Germans would probably be able to cow the Saudis (unless American forces arrived in time to dare Hitler to attack them.) They’d certainly have access to a great deal of oil
Depending on precisely when this happened, Turkey and Iran would both become very important. Turkey would have good reason to secure Northern Iraq before the Germans could arrive — a long-standing Turkish objective — while Iran would probably try to remain neutral or even join the Germans. (Iran was occupied in August 1941, but if the Germans pushed forward hard Iran might rise in revolt.) At that point, the Germans might see value in Iran as a buffer state.
Logistics would remain a major headache for the Germans. Marching all the way into India would seem the ideal way to end the war, but their logistics would need to be built up heavily before they could make their move.
To the east, just how far could the Germans go?
Hitler did come very close to taking Moscow in 1941 (this has, obviously, been hotly debated.) Taking Moscow would not just have dealt a crippling blow to Russian morale, it would also have cost the Russians a large part of their transport infrastructure and the bureaucratic system that kept the USSR running. It’s tempting to joke that shooting the bureaucrats would make the USSR more efficient, but it’s wartime — they need that command economy. Worse, perhaps, large reserves of manpower would be lost. Stalin, assuming he survives the battle, would have to rely on troops drawn from more restive parts of the USSR, troops who might not be remotely trustworthy. And if the Germans make even the slightest attempt to treat the natives well, even as a tactical measure, they are likely to win hundreds of thousands of adherents.
This was, I suspect, Germany’s last chance to win the war outright. Taking Stalingrad in 1942/43 would have certainly hurt the Russians, but it wouldn’t have been enough to keep the Americans from bombing Germany heavily and continuing to supply the Russians with Lend Lease, even if there was no second front. By 1945, America would have atomic bombs — if only a handful. Dropping those bombs on Germany would do immense damage, possibly prompting the military to overthrow Hitler and order a surrender. At that point, the Reich would be doomed.