Imperial Germany goes for merchant U-boats in 1915

Inspired by the other thread, which was about ww2.

https://en.wikipedia.org/wiki/German_submarine_Deutschland

American submarine pioneer Simon Lake visited the Deutschland while she was in Baltimore, and made an agreement with representatives of the North German Lloyd line to build cargo submarines in the US, a project which never came to fruition.[7]


Erich von Falkenhayn, Chief of the German General Staff(Oberste Heeresleitung OHL) since 14 September, concluded that a decisive victory could not be achieved on the Western Front and that it was equally unlikely in the east. Falkenhayn abandoned Vernichtunsstrategie (strategy of annihilation) and attempted to create the conditions for peace with one of Germany's enemies, by Ermattungsstrategie (strategy of exhaustion), to enable Germany to concentrate its resources decisively to defeat the remaining opponents.
https://en.wikipedia.org/wiki/Race_to_the_Sea


U-boat construction by year
1906 (1)
1908 (1)
1909 (2)
1910 (4)
1911 (5)
1912 (5)
1913 (6)
1914 (15)
1915 (51)
1916 (108)
1917 (87)
1918 (90)
https://uboat.net/wwi/types/shipyards.html


Let's say it's late September 1914 when Falkenhayn meets the right people and comes to fully support the idea of using U-Boats to bypass the blockade. An order of two boats is made on October 1st 1914, in order to ascertain the feasibility of the idea (this would be almost 13 months earlier than OTL).

They're finished March 1st, 1915, going by the OTL build schedule, and after a 3-month shakedown begin their journey, as OTL. By late July 1915 they're back in Germany with their cargo.

At that point, the decision is made to dedicate about half of all U-Boats built to this kind of mission, and build them accordingly.

This would mean about 25 boats in 1915 and around 50 in 1916.

Let's say the scheme to build some in America comes to fruition, and we get a further 10-20 boats from there, as well as half o dozen more from places such as Austria-Hungary or Denmark.

How much of a difference would around 80-90 such boats, each carrying 750 tons of high-value cargo across the Atlantic per trip, do for the CP war effort?
 
I have seen a couple of these merchant u-boat threads on here. Still a fun concept though.

My Thoughts:

Germany was just starting to get good diesel engines for the submarines right as war started. If the war had been delayed for a couple of years, I think people would have thought of all sort of ideas for larger and long range submarines then, including merchant trade and including supplying colonies.

The cargo submarines are great for strategic supplies in small quantities. Rubber (for belts in factories). Copper wire for factories, stuff like that.

Also, Good for high value exports like the dyes shipped OTL.

Also, good for politics and diplomacy. Keeping USA neutral. PR. That sort of thing. Sending diplomatic code books.

For bulk stuff like food and nitrates you just don't have enough shipping bulk (90x750) to carry much (and one could see luxuries for rich people taking up much of the cargo space, kind of like confederate blockade running).

Probably 80% of the cargo should be rubber, 10% copper, 10% other stuff. Germany OTL may have been forced to surrender for lack of strategic supplies in 1919, no rubber for gas masks, etc. So the available space should go to that.

Militarily you are basically giving up the war on trade though. So the Allies gain some benefit. Long term keeping USA neutral is likely a war winner and at least avoids complete defeat.

If the Germans totally give up the war on trade, including offensive mining as part of this, the British might have to delay their own blockade rules tightening, which also benefits Germany.

British responses:

The British might beef up their patrols off american coastal cities. Of course America has a zillion small harbors so getting in and out would be still be pretty easy.
The British would try to mine the German harbors (more than OTL).

Questions:
How much supplies did the Germans just get via neutrals or traditional (surface) blockade running, I suspect a lot, the quantities of which just blow away the amounts you are getting via this method.
 
Merchant ships are designed with peace time competitive efficiency in mind. i.e. Slow efficient cruising speed, large, bulky, easy to spot.

But if you are special building WW1 blockade runners. In addition to submarines why not:

A 40 knot regular merchant ship that can out run the old cruisers and AMCs on watch (obviously much cargo space is filled with engines and fuel, and ship has to be narrower), but probably carries more cargo than a sub.

A LST style ship that can be uploaded and loaded from beaches (since ports are guarded any place can be a port). Useful in military landings as well.

A catamaran style ship that can go into shallow areas that larger warships couldn't. Like WW2 Siebel ferries.

A dirt cheap, slow, victory ship style ship, only 20% make it through, but the few that do carry much needed supplies.

Fast warships (like the minelayers the British ran to Malta carrying supplies in WW2), pressed into service to carry strategic supplies. Perhaps with guns removed and thus made merchant. Useful for military purposes too.
 

BlondieBC

Banned
How much of a difference would around 80-90 such boats, each carrying 750 tons of high-value cargo across the Atlantic per trip, do for the CP war effort?

I think you will see most of the benefit in the first 10 or so Merchant U-boats, and almost no benefit after 50. The greatest benefit will be getting your side of the story out to the world. And to bring news of the world back to Germany. A U-boat arriving every 3-6 weeks is plenty. The next major benefit is to bring in some high value items for the war effort. You do make a profit on the dies, but this is not really much of a war effort benefit since Germany did not run out of cash due to the blockade restricting trade.

As to the larger numbers of U-boats, 750 tons or so is just not that much compared to German needs, so the bulkier items can't really come through.

Also, if you were to build 90 merchant U-boats, I would built 10-15 Merchant and the rest as long range warships.

And finally, if you want to use non-German yards, I would like to mention that these ships are not war material. You could just build them in the USA and ship over the submarine crews. If you could get the USA to agree, it presents a nice point of contention between the USA and the UK.
 
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