What would have the impact been on WWII had Germany had a more sizable U-Boat fleet at the start?

Question

From Wikipedia:

At the outbreak of war, the Kriegsmarine had a relatively small fleet of 57 submarines

It took the allies until middle of 1943 to gain an upper hand against the German u-boats. The initial stages of the Battle of the Atlantic were spectacular successes for Germany in spite of initially a very small u-boat fleet.

Intuitively it seems likely that had Germany started the war with more submarines the War in the Atlantic might have gone very differently and potentially caused Great Britain to have been successfully blockaded. The slower numbers allowed allied forces more time to change tactics and develop counter warfare tactics that might not have been allowed had Germany had considerably more submarines initially.

What would have been the impact on World War Two had Germany focused more of their naval production on u-boats prior to WWII?

Answer 1

Outside of the things already mentioned, the Germans would have had a difficult time coordinating the extra wolf packs. In addition to the ever present fear that they could be located by radio detection or code breaking (which turned out to be true after all....), the logistical strain on supporting the U boat fleet would have detracted from many other German projects, especially given the rather chaotic nature of the wartime German economy (Germany didn't really get on a wartime footing until 1943, and was still rationalizing production of many elements as late as the end of the war).

U boats are sophisticated devices, so lots of skilled workers would be needed to continue building the extra U boats, as well as steel and other resources. The U boat pens required an enormous amount of manpower and materials to build, and then there was the issue of resupplying u boats at sea, something the Germans had a great deal of difficulty with (surface tenders were easily intercepted, and "milch cows" (transport U boats carrying fuel and supplies) turned out to be very vulnerable.

I suspect the real answer is that 57 U boats was about the maximum that could be supported by the German war machine, and attempting to build many more would have had very severe knock off effects on other parts of the German military, delaying many of the German plans during WWII.

Answer 2

In all likelihood more submarines would have made America enter the war sooner, or forced the Allies to adopt strategies to deal with them sooner. The best case scenario for the central powers would have been that they had enough U-boats to randomly intercept the Dunkirk evacuation. Perhaps enough submarines would also been able to protect an amphibious assault onto English soil. But probably not.

Answer 3

In all likelihood, had the German submarine fleet been significantly larger and the allies suffered more significant losses, it would have spurred faster development and production of Liberty ships and counter-submarine tactics.

Even if the fleet had doubled in size, the tactics it was using would still have proven insufficient to fully blockade Britain. The allies would have used more Q-ships and armed the Liberty / Victory ships with more anti-submarine weaponry. Losses would have been higher, but they still would have been acceptable (as there was simply no other option).

The largest impact would probably have been the reallocation of B-17 and B-24 bombers for maritime anti-submarine patrols. There would probably also be reallocation and elevated production of destroyers and other anti-submarine ships. This may have diminished the ability for the Allies to strike at mainland Europe and lengthened the war by a few months, but overall the German submarine fleet would have needed to be many times larger to truly turn the tide of war.

Answer 4

Option one: More U-boats come out of the Army/Luftwaffe budgets. With fewer tanks and Stukas, the campaign into France doesn't go so spectacularly well, and the U-boats are mostly used in the North Sea, or short patrols to the Western Approaches rather than in the wilds of the North Atlantic. Overall U-boat campaign - less effective, lacking bases in France.

Option two: More U-boats come out of the Navy budget, impacting production of other ships. Depending on when and how this happens, it could have several different effects, from huge to tiny. For example, it might mean the failure of the invasion of Norway; it might mean that the Royal Navy can deploy more capital ships to the Far East deterring Japan from attacking; it might merely mean that the Arctic convoys do better.

Option three: More U-boats come from some other source. This is the tricky one - where? Where are the materials and finely machined parts coming from? Where's the slack in the budget, and whose toes has the Kriegsmarine stepped on in order to get it? The Nazi government was a fiercely dog-eat-dog world, almost as much as it's view of foreign policy...

It's also worth noting that while the Battle of the Atlantic was only conclusively decided in 1943, the situation was largely under control (from an Allied perspective) in 1941 until the USA joined the war, at which point we got Op Drumbeat and the "Second Happy Time" in US waters...

Answer 5

Apart from expanding the number of submarines available to Karl Donitz and the Kriegsmarine at the start of the war, an increased focus on submarines would likely have resulted in prioritised funding for research as well.

As with speculation along the lines of "what if the Luftwaffe got operational ME-262 jets a year earlier than they did?", it's possible to speculate that an earlier release of technologies such as the Type XXI might have affected the outcome of the war dramatically.

If the Kriegsmarine had more widely implemented the Schnorkel device (allowing submarines to run on diesel engines while submerged) earlier than it did, there might also have been knock on effects.

Same with torpedo technology and countermeasures technology.

Another line of speculation might be "What if the allies took longer to break the enigma code? Or if the axis realised that the code had been broken?"

Answer 6

Had they had more submarines they'd of necessity have had fewer aircraft, tanks, and other ships. Germany was severely resource limited both in raw materials, fuel, and manpower after all.
So had they employed more submarines their land and air forces would have been less capable, maybe far less capable. While this may not have hurt them much against the western allies in the early stages, the campaign against the USSR would have gone bad even sooner, as would the campaigns in northern Africa and maybe even France.

Where they could have gained some benefits maybe is favouring submarine production over the production of surface warships in the pre-war years more than they did.
Then again, this would have allowed the western allies to focus their efforts on ASW assets rather then weapons to fight against the likes of Bismarck and Gneisenau earlier on, fitting out more ASW escort carriers and destroyers instead, which would probably have more than negated any benefits the Germans could have gained rather quickly.

Of course it's all speculation...

A far more effective solution for the Germans to keep the upper hand would have of course been to focus early on on replacing the Enigma machine with a better encryption/decryption system for their military communications. The Enigma was never initially intended for military use and had some rather serious flaws which the English discovered relatively early in the war and which led to after about 1943 every message sent to the submarines to be read before the submarines could act on it, allowing the ASW groups to lie in wait for them, which is what ended the "submarine happy hour".