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.

- - - - -

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.


*: 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.



  1. What was so special about the G3M in comparison to other twin-engine bombers of that period like the Do-17, the He-111 or the SM.79?

    Were the auxiliary cruisers really that effective in comparison with submarines, given that all of them were eliminated with the check-mate system by 1943?
    And could auxiliary cruisers be used in this day and age with satellite reconnaissance and modern communication?

    1. The G3M had oceanic range. The kind of range it takes to fly once around the British Isles with a torpedo and still have a good navigation reserve of fuel (+25% minimum).

      Auxiliary cruisers were effective to some degree (also as a diversion and to make maritime trade less efficient), and just as useless as submarines in a total embargo campaign. Submarines were defeated by 1943 as well, afterwards they needed radical technological change to overcome the self-defeating attrition rate.

      I wrote last month about auxiliary cruisers as blockade enforcers. I cannot determine how much AIS and satellite observation leads to easy ID and tracking of surface merchant raiders nowadays.

    2. 1943 is a general turning point in WWII. It can be argued that the increased American supplies and presence created this situation which quantitatively outmatched Germany on all fronts. In case of the Soviets, American food supplies and trucks enabled them to bring more resources to the fight. How do you consider them a bad investment if they worked fine within the context of a European war, but lost their edge with the US buildup?

      You have a tendency to find the best approaches to solve given problems and then focus on these select solutions. Against active resistance this is an approach thru fewer vectors that can more easily be countered than an approach thru multiple vectors. Achieving an objective thru multiple vectors would include measures that themselves are less effective, but as part of an overall effort stabilize a sustained effort against unexpected counters. The surface navy and the submarines at least hindered somewhat the military buildup on the British Isles. If you consider that as an additional measure to the air campaign, how much effort would it be worth if one prepares for surprisingly effective countermeasures against aerial warfare?

      With the focus on aerial warfare, would a carrier launching aircrafts in the North Sea have helped to reduce German losses during the bombing campaign? Such aircrafts could be used in land warfare as well, making such an investment more versatile than other types of warships.

      And thank you for the interesting read on the military of the Weimar Republic. I suspect they were in part driven by a wish to maximize their capabilities mirroring the greater powers.

    3. University indoctrinated me with some views and ways, such as fighting inefficiency, prioritising the critical path, removing what's irrelevant. People who are familiar with the economics studies curriculum can easily see its influence on this blog.

      Armed bureaucracies have different motivations driving them, as I laid out long ago in posts about the principal-agent problem, Niskanen's bureaucrat and so on. A navy would hardly ever conclude that the best path of action is to scrap its warships and buy land-based aircraft regardless of whether that's the best choice, for example. They view themselves as an organisation with a raison d'être of operating warships, and they'd like to have many of those, powerful ones, and to enjoy big budgets and much prestige.

      BTW, the best precaution against counters is to be versatile. As mentioned above, bombers are the more versatile approach to sink ships than submarines. You cannot support a battle at Sedan with submarine gunnery.
      Moreover, the entire idea of pursuing victory in war by commerce raiding (it was never a real blockade) did not withstand scrutiny, and the 1923...1938 period had defeat in land warfare as a likely possibility. The questionable idea of pursuing commerce raiding should thus have received very little resources until the position on land was acceptable. Hence me drawing the line right behind auxiliary cruisers as commerce raiders.

    4. A modern warship, except a flattop, is usually roughly in the price range of a modern combat aircraft. I would argue that the British, with their carriers that can take on additional aircrafts otherwise used in land warfare, have mostly switched their navy for an airforce at sea, if you break it down by surface combatant investments. It might be hard to stomach for a navy without carriers to switch to land based aviation instead of warships, but bring even small carriers into the equation and it's possible to switch most naval resources to aviation, even land based aviation. I know you are skeptical about the cost benefits of such an approach, because current flattops are rather expensive airfields. But earlier carrier designs were comparatively cheaper and would have provided an easy solution towards an aircraft centric naval approach. There's the article "Buy Fords, not Ferraris." in the proceedings journal of the US navy which critizes these exorbitant costs of floating airfields.
      How cheap would a carrier have to be in your opinion to be considered a cost effective approach as a mobile airfield? And was such a cheap carrier ever feasible?

    5. You're totally wrong about that. The cost of a modern combat aircraft is usually less than € 100 million. A conventional submarine ranges from 300 M to 1 billion, Frigates about 500 M to a billion, destroyers almost a billion. (This is all without munitions, training facilities et cetera.)

      The British have marginal air power on their carrier(s). The planned air wings are two or three dozen F-35 each, and two dozen is much more likely due to the costs. Even the USN has weak carrier air wings these days.
      About 50 combat aircraft, and they have to double as tankers.

      The extra costs surrounding naval air power are excessive. Land-based air power is more than factor two more cost-efficient.

      The similarity of dominant air combat missiles (long range, agile, active radar seeker) with high end area air defence SAMs is such that a fighter as a platform is little more than a substitute for a booster.
      I believe rotary aviation(AEW, ASW) can likely protect oceanic convoys in combination with shipborne missiles. This means container sets for AAW (ESSM, SM-6), ASW, rotary aviation et cetera can be dispersed among multiple cargo ships and the cargo ships could even move in a very dispersed formation instead of a compact convoy.

      Navies need to understand what fighter pilots have come to understand; modern technicized warfare gets decided by electronics and missiles, not platforms. The platforms are exchangeable. We can do most combat aircraft jobs with 40+ years old platform designs, and we could do most jobs with 60+ years-old warship designs - or even container ships.

      Single seat, single engine F-16s were flying bombing missions over Afghanistan while based in Kuwait. We could dominate the North Atlantic's surface with tactical combat aircraft flying from European airbases if we meant to.

    6. Thank you for the correction on ship and aircraft prices. So seaborne aviation is twice as expensive as land borne aviation. If it were 1.5 times as expensive (or lower/higher) would the benefit of a floating airfield pay off? You didn't answer that part of the question.

    7. More than twice as expensive. See the old post, where I arrived at a factor three. I am cautiously claiming 'more than twice' now because it's easy to nitpick about details.

      I only see a legitimate role for fixed wing carriers in oceanic convoying (mostly air defence), and they could be substituted in that role. It requires more calculations to determine which path is cheaper (SM-6 + AEW or CV with fighter and AAMs).

      All that land attack carrier stuff is nonsensical WW2 left over / path dependency and in large part illegal in use anyway.
      Carrier aviation wasn't indispensable over Korea, over Vietnam (which was lost anyway), or over Iraq.
      The Falklands War was nonsense, and even there the land attack carrier aviation component was unnecessary. The marginal and unreliable fighter cover could easily be exceeded by AEW+ SM-6 nowadays.

    8. China builds carriers despite not being path dependent. I think in a conflict between superpowers the rules are created as they go and illegal is not considered a no go area. So you might have overlooked an argument in favour of carriers. This argument might not work for medium sized powers such as Germany.