German naval power analysis for 1923...1939

Germany exited the First World War with a very much reduced navy. Its three most powerful ships were already obsolete by 1906, faced superior French equivalents (still in service for inexplicable reasons) and completely superior French and British battleships (and British battlecruisers). It was not allowed to have submarines, but the British, French and Soviets had or built plenty submarines The only slivers of hope for the German naval position were the Soviet neglect of the Baltic fleet (and other Soviet fleets, a consequence of some anti-Soviet mutinies in the navy) and the hope that the French would not dare entering the Baltic waters with battleships.

Blank_map_of_Europe.svg: maix¿?derivative work: Alphathon /'æl.f'æ.ðɒn/, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

The German navy of the 1920's and most of the 1930's was basically only good for a naval blockade of Poland, and that was rather pointless considering the strategic situation on land and the possibility that Polish arms imports by sea might be escorted by a foreign great power navy. 

flag of the Reichsmarine 1921-1935

I suppose the ships and boats of Germany in the 20's and 30's can be divided into groups, with very distinct utility and justifications.

Group A: Coastal forces

image linked from kbismarck.com

(1) minesweepers (the German approach to it was also usable as a coastal escort of little capability)

(2) coastal minesweepers (smaller and cheaper boats mostly useful for sweeping marked lanes in front of a port over and over again)

(3) torpedo recovery boats (for training, could also be done by the minesweepers)

(4) net layers (to close and open net barriers near and in ports, could be improvised with very small civilian ships)

(5) defensive minelayers (could be done by modified coastal cargo ships in wartime as done during WW2, so the peacetime navy only needed some testing & training opportunities. Many non-specialised craft had mine laying rails for this.

Vorpostenboot / picket boat, image linked from german-navy.de

(6) picket boats (most of these would be wartime production or modification, technically similar to coastal fishing trawlers)

(7) motor torpedo boats (which make close port blockades too dangerous with potential nighttime surprise torpedo attacks and also make passing the Danish straits between North Sea and Baltic Sea very dangerous)

(8) minebreakers / hull-mounted influence minesweepers (sweeping mines by triggering them itself, preferably at a survivable distance ahead)

(9) 15 cm coastal artillery Most German coastal cities are quite inaccessible to accurate coastal bombardment by geography, unless one assumes undisturbed operation of an aerial forward observer. 15 cm was and is a sufficient calibre to defeat smaller units that might come close enough to such coastal cities for line-of-sight fires, or dare to enter rivers.

15 cm C/28, photo linked from weaponsandwarfare.com, hat tip to Mitch

Group A is mostly what you could even have in law enforcement or civilian institutions. Minesweepers evidently were civilian in the immediate post-WW2 years, for example. Motor torpedo boats (and coastal minesweepers) would have been great for customs, police and maybe even civilian search and rescue, and easily converted in a few days for military use. The coastal artillery could have been under army control*, as was later partially done during WW2.

The ships and boats of group A were relatively cheap and dual purpose. They could be justified due to their low cost.

Group B: Blockaderunning enablers

Blockaderunning would be feasible in a conflict with France (albeit this would have been a quick decisive defeat on land until about 1936) in three ways:

(1) Blockaderunning cargo ships could exploit Norwegian territorial waters for safety and then sprint just the final section from Oslo to German Baltic Sea ports.

(2) The blockaderunners would have to run roughly the double distance in case France does not respect neutral Norwegian territorial waters, and could be intercepted by cruisers, auxiliary cruisers and destroyers between Norway and Scotland. The blockaderunning would thus likely happen in severe weather (and new moon nights) or during wintertime (long, preferably new moon nights) with possibly still bad weather (especially rain).

(3) Wartime production unarmed trade submarines (as done in WWI, suitable only for cargo of great value relative to its volume and for natural rubber import).

Blockaderunning enablers would be destroyers (escort mostly against the dozens of French submarines, though for lack of a sonar until the mid-1930's mostly by spotting rather than by engaging them) which would not fare well in severe weather, light cruisers (good against destroyers, auxiliary cruisers, and at most against light cruisers or at night heavy cruisers, but still not promising for severe weather) and heavy cruisers (basically only useful against cruisers and against destroyers in daytime).

The French fleet had no fast capital ships until the mid-30's and could not have maintained more than 50% of its capital ship, cruiser and destroyer strength on blockade patrol. Blockaderunners of 21+ kts speed would have been able to slip by the battleships in good visibility if enabled by good scouting. Light cruisers were still considered to be the best scouts, as aircraft were not very capable until the mid-1930's, and Germany could only have used modified passenger aircraft for naval scouting till the mid-1930's anyway. Destroyers were faster and cheaper than light cruisers, but slower in rough seas and generally much weaker in a gun duel.

The few German heavy cruisers with 20.3 cm guns built in the mid-late 1930's might be considered suitable for the blockaderunning-enabler (escort) task.

The only really reliable approach against a French naval blockade would have been to do some clandestine overseas trading through the Netherlands, Denmark, Sweden and for clearly German export goods with wartime-built trade submarines. The blockaderunning enablers were thus not a 100% necessity.

Group C: Diversion for blockaderunning-enabling

German 28 cm SK C/28 triple turret. The first triple turret munition transportation issues solved for a rate of fire about equal to twin turrets. image linked from navweaps

 

Three heavy cruisers with unusually large primary artillery calibre of 28 cm (actual calibre 28.3 cm) were a subject of great political debate in the late Weimar Republic and meant as treaty-legal replacement orders for the three pre-Dreadnoughts. Their 28 cm triple turrets were spectacular for cruisers, but more spectacular (and less obvious to the public) was their diesel engine-enabled range, which permitted mid-Atlantic operations from German ports even without refuelling at sea. The actual impact on French maritime shipping could not possibly be considered important to a war effort, so the only flimsy excuse for their existence would be a diversion; drawing battlecruisers and heavy cruisers away from the far blockade task in the North Sea. The problem with this was that the only French cruiser with the speed and range for hunting them was the Algérie, a rather inferior contemporary heavy cruiser that would not have been sent out to chase such a German ship alone. It would rather have been sent after an auxiliary cruiser. The only French ships with the speed, range and combat ability to hunt these German raider cruisers were the two battlecruisers built in response to them. These two battlecruisers were also incredibly useful for a more capable North Sea blockade patrol and might not have existed if Germany hadn't built these three heavy 28 cm gun cruisers.

Diversion only works if the opponent doesn't understand that not being distracted is more advantageous for him or if the diversion is extremely cost-efficient. This and the inherent illogic of the three 28 cm cruisers rendered them unnecessary.

Group D:  Coastal submarines

Coastal submarines (type II) eventually mostly served as training boats, but they could be considered a complement to the motor torpedo boats in that they would deter entering the Baltic Sea in force and deter close blockades. They were not needed for either role when they were commissioned, for at that time non-dedicated aircraft were able to deter such French naval actions.

Redundant to air power and motor torpedo boats, the coastal submarines were an unnecessary, avoidable and dangerous irritation of the UK.

edit: In case you're confused as I previously mentioned they were not allowed by Versailles Treaty to have submarines: Here's the background story.

Group E:  Lots of prestige ships and boats

These ships were supposedly useful for commerce raiding and submarine blockade in the Atlantic.

This group includes the four battleships, which were near-irrelevant for commerce raiding and unnecessary for blockaderunning-enabling against the French navy due to the availability of air power by the time of their commissioning.

This group also includes the oceanic submarines, all of which were only pushing the British into thinking of Germany as primary antagonist (which was not as self-evident as one would think today, for there was still the Soviet Union and Italy was the European troublemaker #1 in 1936-1938, which is nowadays largely forgotten).

None of these made sense. A war against France without war against the UK could not possibly be influenced much with commerce raiding or submarine efforts, as France could trade through the UK (easily secured English Channel) and the Mediterranean. A war against both France and the UK looked hopeless during the entire 1920's and 1930's. The French collapse in 1940 was contrary to any justifiable expectations and contrary to the strategic imbalance, which greatly favoured the Western powers. A naval blockade against the UK after a defeat of France could much better be done by air power (see Mitsubishi G3M abilities, first flight 1935) than by submarines, as Germany could more quickly produce thousands of long range bombers than hundreds of oceanic submarines. Furthermore, the effect of ASDIC (sonar) was unpredictable, making any bet on submarines at least as risky as a bet on the much more versatile air power.

Furthermore, Germany would first have needed to defeat and occupy France before it could hope to defeat the UK with a naval blockade, so using versatile air power that's both useful for defeating France and defeating the UK made more sense. Submarines were not very capable at shelling French land forces.

I consider any opinion that there was a near-success of the submarine blockade during WWI to be delusional. The UK was at no time even close to the import restrictions that Germany suffered from throughout the war. Germany had a famine in the winter of 1916/1917 before Ukrainian agricultural resources were captured. The UK didn't even come close to the scarcities faced by Germany outside of this famine. A naval blockade against the UK could not possibly be decisive as long as the easily-secured Portsmouth-Le Havre route was available for trade, enabling even distant overseas trade through the French Mediterranean port of Marseilles. A successful naval blockade of the UK would thus have had hostile control of Northern France as a necessary condition.

The expensive and provocative group E seemed to lack sufficient justifications.

Group F: Armed merchantmen/auxiliary cruisers

The French had very little ocean patrolling ability, so even the North Atlantic would have been a promising area of operations for such raiders if the UK stayed neutral. The French ability to hunt and stop auxiliary cruisers on other oceans was negligible.

anatomy of most successful German WWI raider SMS Wolf (with aircraft "Wölfchen"), image linked from squadronshop

It didn't take much to create an effective auxiliary cruiser for commerce raiding. You needed a preferably fast (17+ kts) ship with very good endurance at sea, some holding cells for prisoners, cranes, at least one 10.5 cm or bigger gun. Luxury features would be extra crew quarters for prize crews (and prisoners), surplus guns to turn prize ships into additional auxiliary cruisers, strong gun or torpedo armaments capable of surprise-killing a cruiser, beyond-the-horizon passive sonar or a scouting aircraft** with associated equipment (especially a catapult). Such auxiliary cruisers did thus not require much expense in peacetime. Even the crew could mostly be drawn from conscripted merchant marine personnel and would not require much if any expense in peacetime.

Group F needed no peacetime justification, for it incurred hardly any expenses (if any expenses at all) in peacetime.

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I wrote a rather polemic text about the stupidity and uselessness of German navies before, but this more in-depth look shows that at most some paramilitary coastal forces were ever required and at most a modestly-budgeted navy similar to the Weimar Republic's navy could be justified, albeit not be proved to be necessary.

This lengthy blog post still doesn't come close to a comprehensive and 100% conclusive argument, but I did what the format permits (hopefully) without being too boring for almost all readers. Moreover, naval-interested readers will likely have noticed the completely different approach and narrative of this blog post compared to just about all literature on the subject. Most literature on the ships and navies of the era has an almost fanboi-ish approach by comparison. It doesn't analyse the actual needs, or missions, or budget justifications. Some admiral issued a requirement for a certain ship? That's good enough for just about every author. I like the excellent books of M.J. Whitley in particular, but he, too, doesn't cover non-technical aspects much and only mentioned very briefly what capabilities the men behind the procurement wanted.

S O
defence_and_freedom@gmx.de

*: It could have been under army control, save for the Versailles Treaty restrictions which rendered such an option nonsensical. I'm describing here why capability-wise hardly any naval establishment was needed. The political-legal restrictions enforced another reality.

**: Such floatplanes were incredibly useful not just for scouting. They even tried (and presumably sometimes succeeded) to cut the radio antenna cables of ships so they could not emit an emergency radio message.

P.S.: The German cruiser designs of the Interwar Year were all badly flawed:

light cruiser Emden: unusually good range, but inefficient and poorly protected artillery concept

later light cruisers: unsuitable for severe weather, built more for show than performance, could not withstand battle damage well, too large crew

28 cm heavy cruisers: slower than most new foreign cruisers, cost-inefficient, unsuitable for severe weather, poor secondary and anti-air artillery, armour insufficient as protection against all heavy cruisers, too large crew (albeit the excess could be used to man prize ships on a raiding patrol)

20.3 cm heavy cruisers: unreliable propulsion (due to very high steam pressures), fuel inefficient even by steam propulsion stnadards, poor anti-air artillery (insufficient though better than what the French and British heavy cruisers had), armour could be penetrated by French Algérie at some relevant distances without being able to penetrate Algérie's deck or belt armour as well, too large crew

It's remarkable that these ships were poor at severe weather, even though this would have been ideal weather for blockaderunning. The German navy appeared to have been too centred on pleasant peacetime cruises close to German ports. The  post-Emden light cruisers in particular were built more to look good on paper than to excel in combat, a 180° reversal of German pre-WWI naval design philosophy.

Likewise, the Japanese overloaded their ships to the point of some of them capsizing in storms. The Italians exaggerated (the importance of) the speed of their cruisers. The French had very flawed guns on their early super destroyers. Americans and Italians in particular had heavy cruiser turrets with barrels so close to each other that the horribly large salvo dispersion disarmed the ship for long range duels. Flawed ships were common, but it's striking that the poor seaworthiness of German cruisers was contrary to the least weak justification of their existence.

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