Better German naval strategy 1930-1945?

[z42]

The Weimar Republic was starting to come apart - if the National Socialist party failed, the next strongest party would have filled the void.

That party was the Social Democratic Party (SPD)...

Yes, and..? Are you saying the SPD wouldn't have been up to the task? I'm not that familiar with the Weimar-era SPD, but seems the SPD and CDU have taken turns ruling Germany after WWII. And seems they have done ok, Germany today enjoys a high standard of living, and at least so far they haven't started WWIII either.

 

[z42]

It's very similar to saying Japan would have won at Midway if they hadn't started the war with America. They wouldn't have, because there wouldn't have been a war. But of course, where would they get oil? Tin? They couldn't get those resources without foregoin their invasion of China, which was predicated much on seizing Chinese rice to feed the burgeoning Japanese population, Again, agricultural issues.

Yes, they couldn't have continued with their China invasion and still being able to access world trade. Choices, choices.

What you advise is not a "war-winning" strategy, but a peace-keeping strategy, which is all fine and well.

Sometimes you have to realize that the only way to win is to not play.

But when you consider that Germany could not feed itself from its own agricultural output (just like Japan) and still had to import foodstuffs, and that that German industry devoted to domestic farm tractors is not industry devoted to generating foreign currency exchange, what do you do then? Your economy is going to overheat anyway, as you're spending a lot internally and still piling up external debt while you sort out your farming equipment.

The argument is that agricultural mechanization and synthetic fertilizer could have provided a vision for Germany to feed itself, as an alternative to the dreadful nazi Lebensraum vision of conquering and enslaving neighboring countries and getting enough food that way.

As for foreign exchange, that is undoubtedly a problem. But it's even more a problem for a military buildup as well, considering all that military hardware is, from an economic perspective, deadweight. In reality Germany solved the foreign debt problem by starting the war, otherwise it would have defaulted on its debts. If that's not an option, the government would have to be more careful about taking on more debt.

 

[SaparotRob]

The greatest fast battleships still afloat! But, they never contributed much to WWII, did they?

Of course, they didn't know that when they were ordered. But if a much greater u-boat threat would have prioritized building a million ton of ASW focused hardware before laying them down, by that time they might have seen that the future belongs to aircraft, and subsequently converted the Iowa order to Essexes, or even Midways?

 

[Zmauky]

hmm, we strayed a bit from the thread title, but still...
Aside from the reasons for Japan's entry into the war, I think the biggest mistake was the way they chose. Instead of following a national plan of conflict and organising the mother of all battles (say by taking the Philippines and dragging America into a war in Southeast Asia on their home turf ) they decided to anger them.
And Germany ... well, the navy certainly lacked the Lipetsk equivalent of the Luftwaffe. Submarine designers manage to stay in the game, but the Allied post Versailles Commission quite successfully stifled the development and design of other classes of military ships and equipment (for example, by banning the development of high-powered marine diesel engines for battleships or stoping development of big guns).
Well, some equivalent of a school that would encourage development and ideas... (or let's say chance to find that their torpedoes don't work as they should).
How much would they help the Russian side ... well, every step of Russia directed towards the sea is a step backwards for the their ground forces (or at least the deprivation of resources).
That Germans started well in that direction (but did not continue) is the fact that the most deserving factor for the annulment of the Treaty of Versailles... was the class of pocket battleships (an ideal example of thinking out of the box). And that is the only way to outplay an opponent with more ships and larger production capacities. The ground army was successful in this for the first three years of war.
In fact, perhaps the most important question is not whether the Kriegsmarine should have had more submarines or battleships or something else than what their real strategies should have been. Somehow it seems to me that Bismarck's trip to the Atlantic or the twins' walk across the channel (to name just two examples) are actions that did not have some strategic idea what they were supposed to achieve. Mostly too few well-thought-out moves (such as the aforementioned Drumbeat) that had far greater consequences in terms of engaging allies.

 

[marathag]

But when you consider that Germany could not feed itself from its own agricultural output (just like Japan) and still had to import foodstuffs, and that that German industry devoted to domestic farm tractors is not industry devoted to generating foreign currency exchange, what do you do then?

International Harvester made Halftracks, anti-tank guns and aerial Torpedoes
Massey-Harris made light tanks.
John Deere made High Speed Artillery Tractors and Transmissions and Final Drives for M3 and M4 Tanks, about half of all made.
Alice Chalmers made artillery tractors, cannon parts, and turbines and pumps, some that were used with the Manhattan Project.

And so on.

Factories making Agricultural equipment can do other products if needed.

A big problem of both Germany and Japan, were too traditional, and farms were just too small to get decent economies of scale.

Average size of of a Japanese Farm was 2 acres.
1% of German Farmers had more than 250 acres. 3 million German Farmers had farms of less than 5 acres. Farmers with 5- 50 acres was 35%
The average Farm size in the USA was 550 acres.

Farmers are slaves to the Calendar. You have time to plant, and a time to harvest.

Horses and then Tractors allowed a Farmer to plant and harvest far more land with machinery during that time limit set by nature.

That increases productivity. Then add in the US eager adoption of Chemical Fertilizers and high yield seeds, a single US Farm needed far fewer workers to produce more food than in Germany and Japan.

Farms don't have to generate foreign currency, if they reduce monies spent on importing food from other countries.
And when needed, those Factories can convert to War Production.

 

[Thumpalumpacus]

Farms don't have to generate foreign currency, if they reduce monies spent on importing food from other countries.

Until you start a war, and find again that your farming isn't enough to feed the population, and now you've lost those peacetime savings and have lost much, though not all, in the way of imports. You don't want to go into war already on deficit spending, if at all possible. And if you do, it had damned well better be short and sharp.

But going to war against a nation who can switch civilian to military production, and has a tax base to pay off incurred debt after the war is over, probably not a good idea, especially when your economy is overheated a full year before the war starts, as was the case with Germany and to a lesser extent Japan.

And when needed, those Factories can convert to War Production.

Sure. Then you have to ask, "How many factories and workers do we have, and how many factories does our enemy have?" Another useful question is "How will we pay for this?"

Going back to the thread's topic, German naval equality is never going to happen and that means German naval strategy will always be playing catch-up. They have neither the money, the industry, the labor pool, or the naval manning to match the RN, unless they want to denude themselves against Russia.

 

[z42]

Aside from the reasons for Japan's entry into the war, I think the biggest mistake was the way they chose. Instead of following a national plan of conflict and organising the mother of all battles (say by taking the Philippines and dragging America into a war in Southeast Asia on their home turf ) they decided to anger them.

Hmm, I have a hard time understanding how conquering the Philippines would not anger the US?

And Germany ... well, the navy certainly lacked the Lipetsk equivalent of the Luftwaffe. Submarine designers manage to stay in the game, but the Allied post Versailles Commission quite successfully stifled the development and design of other classes of military ships and equipment (for example, by banning the development of high-powered marine diesel engines for battleships or stoping development of big guns).

Versailles and the post-WWI economic meltdown led to a loss of institutional knowhow how to build warships, and is probably the main reason why German WWII surface warships were, if not outright awful, at least pretty inefficient in terms of the capabilities they packed into their displacement.

the class of pocket battleships (an ideal example of thinking out of the box). And that is the only way to outplay an opponent with more ships and larger production capacities.

The pocket battleships were a good first try for the task they were designed for, countering French ships trying to blockade East Preussen, and arguably they were better suited for surface raiding than any of their other heavy surface warships. But when you look closer, one sees that packing big guns in a limited displacement necessitated some very big sacrifices, particularly wrt speed and armor.

In fact, perhaps the most important question is not whether the Kriegsmarine should have had more submarines or battleships or something else than what their real strategies should have been.

Indeed. That's even spelled out in the title of the thread! What is the strategic purpose of the KM? And once you have that down, then you build the fleet to implement that strategy.

Somehow it seems to me that Bismarck's trip to the Atlantic or the twins' walk across the channel (to name just two examples) are actions that did not have some strategic idea what they were supposed to achieve.

While we all know how Bismarck's first mission ended, I think there was a method to the madness. A few months before Bismarck's mission, Scharnhorst and Gneisenau slipped out into the Atlantic and sunk 22 merchants, with no losses on the German side. RN capital ships chased all around the north Atlantic trying to catch them, unsuccessfully. Operation Berlin (Atlantic) - Wikipedia

So why not try to repeat that great success with the Bismarck? Evidently they thought they could replicate that success, not realizing how lucky Operation Berlin had been?

And the channel dash follows logically from the above. After the sinking of the Bismarck, the KM apparently came to the conclusion that operating large surface warships in the Atlantic is too dangerous. But after Operation Berlin S & G were stuck in Brest, along with PE which had survived the Bismarck operation. So they needed to bring them home. Apparently most planning was focused on going around the UK, until they figured that dashing through the channel is such an outrageous idea it might actually work.

 

[ThomasP]

re Japanese farming in 1940 vs US farming in 1940

FWIW

Although it is sometimes not too difficult to compare the efficiency of the farming methods used, it should be noted that it is extremely difficult to do so when the main differences were the types of crop, the climate, and the total amounts of arable land.

Japan grew rice for the most part (over 90% of their grain crops) and managed over 93 bushels/acre in 1940.

The US grew mostly corn, wheat, oats, barley, and soybean, managing about 30, 29, 28, 22, and 20 bushels/acre respectively.

It was not until WWII started, and the US government began large scale investment in farm related support industry and initiated large scale subsidies for farmers, that crop yields began to increase sharply. It was not until the 1950s that the US crop yields of wheat began to outpace the pre-war Japanese wheat crops in terms of bushels/acre.

The reason that Japan could not feed itself really had nothing to do with efficiency, and everything to do with the amount of land available for farming of various crops vs the population. Japan's total arable land for cash crops was less than the arable land in some US states such as Iowa and Ohio.

Also, note the difference in amount of arable land per person.

Japan_______~16,000,000 acres arable or ~17% of total land area for ~73,000,000 people, or 0.22 acres/person
_____________ ~8,000,000 acres of rice, at 93 bushels/acre
_______________~138,000 acres of corn, at 24 bushels/acre
_____________ ~1,120,000 acres of wheat, at 33 bushels/acre (limited amount of land usable for wheat due to relatively wet climate)
_______________~340,000 acres of oats, at 42 bushels/acre
_____________ ~1,800,000 acres of barley, at 43 bushels/acre
_____________ nil rye
_____________ ? acres of soybeans (I could not find acres used for soybean production in Japan, but in terms of bushels they produced about 1/4 of what the US did. Presumably this acreage accounts for a significant amount of the acreage not listed above.)

NOTE that the above information is for the Japanese home islands only. It does not count crops grown in Manchukuo.

US________ ~320,000,000 acres arable or ~7% of total land area for ~132,000,000 people, or 2.40 acres/person
_____________ ~1,000,000 acres of rice, at 50 bushels/acre
____________~88,000,000 acres of corn, at 30 bushels/acre
____________~58,000,000 acres of wheat, at 29 bushels/acre (includes summer and winter crops)
____________~33,000,000 acres of oats, at 28 bushels/acre
____________~12,600,000 acres of barley, at 22 bushels/acre
_____________~3,800,000 acres of rye, at 11 bushels/acre
____________~10,000,000 acres of soybeans, at ~20 bushels/acre (I could not find the specific bushels/acre for the US or Japan)

Germany____~32,000,000 acres arable or ~16% of total land area for ~71,000,000 people, or 0.45 acres/person
_____________ nil rice
_____________ nil corn
_____________~6,000,000 acres of wheat, at 34 bushels/acre
_____________~8,000,000 acres of oats, at 58 bushels/acre
_____________~4,800,000 acres of barley, at 40 bushels/acre
____________~12,000,000 acres of rye, at 31 bushels/acre
_____________ nil soybeans*

NOTE that the above information is for the country of Germany proper.

* Interesting bit re soybeans and Germany: "1933 – The Germans are now the world's largest soybean importers, buying most of their soybeans from Manchuria. But as early as 1933 the Germans realize that dependence on Manchurian [ie from Japanese held Manchukuo] soya, which is almost entirely brought by sea to German ports, would be dangerous in time of war and that reliance on Trans-Siberian railway consignments, even assuming Russia to be friendly, would also be precarious. For this reason as soon as Hitler comes to power the Germans take steps to develop the production of soybeans in Romania and other Balkan countries. The large chemical group I.G. Farben Industrie [the German Dye Trust], with the full support and encouragement of the Reich Government, begins preparations in 1933 to promote the cultivation of soybeans in Romania. Thousands of tons of seed are taken into the country. In 1934 a Romanian company, the Soja S.A.R., is incorporated in Bucharest (the capital of Romania) with German capital for producing and trading in the beans. The company provides Romanian peasants with seed and bacteria; it makes the necessary advances against future delivery; and it looks after technical instruction in soya cultivation. Its activities reach into almost every village in those districts where production was possible"

NOTE that most of the information is from US and international grain market records.

 

[Zmauky]

Hmm, I have a hard time understanding how conquering the Philippines would not anger the US?

There is a big difference whether America entered the war because of "some islands over there" (which should have gained independence in 1946 anyway) and with Roosevelt, whose pre-election promise was that he would not go to war (even though he did everything the opposite) and the desire for revenge due to humiliation in PH. From memory Gallup's pool jumped from just under 50% to practically 100%. They are not historically the same times and cannot be compared, but Vietnam ....
In addition, the Japanese idea of the conflict was based on the victory at Tsushima
- so drag the opponent far, to your field and carve him in one decisive battle. Yes, the USA has/had bases in the Philippines, but Japan has shown that it can handle it (and with no surprise if we remember KG V and Repulse). They didn't even need to conquer the Philippines, they could have just gone to the Dutch East Indies. I know that there were joint plans of UK DEI USA against Japan but the question is how Roosevelt would be able to sell congress a declaration of war because of other people's colonial possessions. Yes, sooner or later he would succeed, but under what conditions (and with what support from voters and Congress).
----
I mentioned Lipetsk (in the USSR) because the future Luftwaffe trained pilots there, but also Junkers and Heinkel designed (and had workshops) for the planes that the Russians produced in series. Perhaps the German submarines were not the best but (I assume mainly due to) continuous development (and production) kept them at/or near the top. It's the same with aviation, so why not the same thing with ships? I'm not sure about '30 (but there were plans in the USSR to save a couple of capital ships), but after the Molotov-Ribbentrop Pact, the CCCP definitely showed interest.
------
Yes for operation Berlin - there was a method to the madness, but even the wiki says "Its main goal was for the battleships to overwhelm the escort of one of the convoys transporting supplies to the United Kingdom and then sink large numbers of merchant ships. The British were expecting this given previous attacks, and assigned battleships of their own to escort convoys. This proved successful, with the German force having to abandon attacks against convoys on 8 February as well as 7 and 8 March."
Repeating something that wasn't even a surprise...
----


In general I think that the biggest problem of the Kriegsmarine was Hermann (and Raeder).

Zenker showed a path that Raeder did not know/was able to follow.

And aviation...
He 111J was supposed to be a dedicated anti-ship variant that was cancelled, so what (at the critical initial moment) would have been contributed by a Geschwader or three long ranged maritime Do 19 or even just a regular Fw 200. Not to say (for purely wiff reasons) that we might be reading about the naval He 112 and Fw 187.
Not to mention the later support for submarines.

Strategic purpose of the KM?
- Securing the Baltic (from the RN and the Russian fleet) - successful
- Support for ground operations in the Baltic and the North Sea and elsewhere in the range of the invasion of Norway (more or less successful) and Russia (0 points - an example is the successful evacuation of Russians from the Baltics, not to mention Leningrad).
- marine mammal operation insurance (forbidden word on a certain forum) 0 points
- pressure on the UK (Battle of the Atlantic) - ok until mid-1942 when they lost the technological battle
- Mediterranean ... with RM no one expects big KM ships but those couple of dedicated anti-ship Geshwaders ... what would Crete and Malta and Pedestial and ... Suez look like
- The Black Sea ... the same thing with the non-existent Russian fleet (all these anti-ship Geshwaders) and logistics via ships - how would the Crimean operation or the Blau pass?

Conclusion - 1 to 5(6,7) because you can not count 0.5

 

[Shortround6]

Strategic purpose of the KM?

Point of the thread and a nice summation.

- Securing the Baltic (from the RN and the Russian fleet) - successful
- Support for ground operations in the Baltic and the North Sea and elsewhere in the range of the invasion of Norway (more or less successful) and Russia (0 points - an example is the successful evacuation of Russians from the Baltics, not to mention Leningrad).

German goals changed over 20 years but dealing with the Russians/Soviets are an often over looked consideration. Granted the Soviet fleet was scattered over several oceans/seas and needed major miracles to actually meet up in one area, but the Soviet Baltic fleet was a problem for the Germans in the 1920s and after fading in the 1930s it seemed to be on the upswing in the late 30s. Maybe if the Germans had not laid down the Bismarck and Tirpitz the Soviets would not have laid down the Sovetsky Soyuz class of super battleships (actually completing them might be a different story).
However the Soviets were building cruisers with 7.1in guns and several dozen modern destroyers in the 2nf half of the 30s. Some in the Baltic.

marine mammal operation insurance (forbidden word on a certain forum) 0 points

Well, Sea Lion was pretty much a lost cause without a much, much bigger fleet and Air Force.

- pressure on the UK (Battle of the Atlantic) - ok until mid-1942 when they lost the technological battle

And in 1936-1941 the shift in technology could not be foreseen and the British were expending a crap load of resources on that battle instead of being able to use them elsewhere.

- Mediterranean ... with RM no one expects big KM ships but those couple of dedicated anti-ship Geshwaders ... what would Crete and Malta and Pedestial and ... Suez look like
- The Black Sea ... the same thing with the non-existent Russian fleet (all these anti-ship Geshwaders) and logistics via ships - how would the Crimean operation or the Blau pass?

Here we are getting into what the Luftwaffe should have done vs what the Kriegsmarine should have done. Kriegsmarine didn't even have "control" over their own float planes let alone ground based Maritime search/attack aircraft.
Using aircraft instead of ships is a different strategy (and one fought in several nations or the fighting between which air force should perform certain missions and control certain production sources)

Even in WW I both sides would occasionally attack/shoot up their opponents fishing fleets.

Germans might decide not to invest quite so heavily in the navy in the 1930s, but they cannot abandon it and in truth they can't do a lot less than they did. Not build Tirpitz and Graf Zeppelin? cut down on U-Boat construction from mid 1943?

 

[marathag]

Not build Tirpitz and Graf Zeppelin? cut down on U-Boat construction from mid 1943?

Tirpitz soaked up far more British resources that what it took to build her.
That said, would have just built Bismarck, and just kept here as the threat fleet. No 1940 raid into the Atlantic. Use the resources to build a third Scharnhorst with 15" guns.

Wouldn't have put down an ounce of Steel for G.Z. Make a deal with Japan and buy Kaga from Japan in 1936, and license to build Kates

U-Boats have lost the Battle of the Atlantic, so is pointless to build more.

 

[GrauGeist]

As the Reichsadmiral, how would you have known the U-Boots would lose the battle of the Atlantic without a magic lamp?

Sitting back, eighty years later, you have the luxury of seeing how the strategy unfolded, but at that point in time, no one knew...

 

[z42]

Yes, the USA has/had bases in the Philippines, but Japan has shown that it can handle it (and with no surprise if we remember KG V and Repulse). They didn't even need to conquer the Philippines, they could have just gone to the Dutch East Indies. I know that there were joint plans of UK DEI USA against Japan but the question is how Roosevelt would be able to sell congress a declaration of war because of other people's colonial possessions. Yes, sooner or later he would succeed, but under what conditions (and with what support from voters and Congress).

That's a kind of interesting scenario, what if Japan had bypassed the Philippines and gone straight for the DEI? Of course, when eventually the US joins the war the Philippines would be a major thorn in their side, and could block a lot of shipping.

In general I think that the biggest problem of the Kriegsmarine was Hermann (and Raeder).

Zenker showed a path that Raeder did not know/was able to follow.

Reading up a bit on Raeders interwar career it seems here we have someone with a serious chip on his shoulder, and convinced that the path to German greatness was in becoming a major naval power. A look at a map and the post-WWI worldwide naval strengths should have provided a much needed reality check.

And aviation...
He 111J was supposed to be a dedicated anti-ship variant that was cancelled, so what (at the critical initial moment) would have been contributed by a Geschwader or three long ranged maritime Do 19 or even just a regular Fw 200. Not to say (for purely wiff reasons) that we might be reading about the naval He 112 and Fw 187.

A long-range escort fighter could have been useful to protect their maritime strike packages once the Allies start deploying more carriers around their convoys? Would have been cheaper than developing their own carrier-based aviation, for sure.

Strategic purpose of the KM?
- Securing the Baltic (from the RN and the Russian fleet) - successful
- Support for ground operations in the Baltic and the North Sea and elsewhere in the range of the invasion of Norway (more or less successful) and Russia (0 points - an example is the successful evacuation of Russians from the Baltics, not to mention Leningrad).
- marine mammal operation insurance (forbidden word on a certain forum) 0 points
- pressure on the UK (Battle of the Atlantic) - ok until mid-1942 when they lost the technological battle
- Mediterranean ... with RM no one expects big KM ships but those couple of dedicated anti-ship Geshwaders ... what would Crete and Malta and Pedestial and ... Suez look like
- The Black Sea ... the same thing with the non-existent Russian fleet (all these anti-ship Geshwaders) and logistics via ships - how would the Crimean operation or the Blau pass?

Conclusion - 1 to 5(6,7) because you can not count 0.5

Good points. I'll note the Montreux convention was in force by then, prohibiting warships from transitioning through the Bosporus. So whatever naval assets they are deploying in the Black Sea has to be brought there over land, or built in place. I believe they did disassemble some small u-boats, transferred them by rail, and then assembled them again on the Black Sea coast.

 

[z42]

German goals changed over 20 years but dealing with the Russians/Soviets are an often over looked consideration. Granted the Soviet fleet was scattered over several oceans/seas and needed major miracles to actually meet up in one area, but the Soviet Baltic fleet was a problem for the Germans in the 1920s and after fading in the 1930s it seemed to be on the upswing in the late 30s. Maybe if the Germans had not laid down the Bismarck and Tirpitz the Soviets would not have laid down the Sovetsky Soyuz class of super battleships (actually completing them might be a different story).
However the Soviets were building cruisers with 7.1in guns and several dozen modern destroyers in the 2nf half of the 30s. Some in the Baltic.

The Kirov class was a pretty compromised design. Very little armor, and the gun turrets were very cramped so they had a low rate of fire (around 2 shells/minute, about what you'd expect from a BB size gun), and shell dispersion was large due to the barrels being too close to each other. A 1930 era treaty light cruiser would probably be more than a match for them in a one-vs-one engagement. They were very fast though. And the Germans might not have been aware of the gun issues, though.

Here we are getting into what the Luftwaffe should have done vs what the Kriegsmarine should have done. Kriegsmarine didn't even have "control" over their own float planes let alone ground based Maritime search/attack aircraft.
Using aircraft instead of ships is a different strategy (and one fought in several nations or the fighting between which air force should perform certain missions and control certain production sources)

Well, the topic is "better NAVAL strategy", not "better KM strategy". So spending more resources on (land-based) maritime recon and strike is an option, even if it were to be done under the auspices of the LW rather than the KM.

I'm not sure that there's a clear answer whether it's better for land-based maritime aviation to be under the control of the navy or the air force in general. Probably the answer ends up being more a result of inter-service turf wars.

 

[z42]

Tirpitz soaked up far more British resources that what it took to build her.
That said, would have just built Bismarck, and just kept here as the threat fleet. No 1940 raid into the Atlantic. Use the resources to build a third Scharnhorst with 15" guns.

They could have built a third Scharnhorst, even with the 28 cm guns, instead of the Bismarck and Tirpitz. To be used as a RAF bomb sponge in Norway, and forcing the Allies to deploy BB's to escort the Arctic convoys.

Wouldn't have put down an ounce of Steel for G.Z. Make a deal with Japan and buy Kaga from Japan in 1936, and license to build Kates

1936 is probably too late to start developing a naval aviation capability? And the Japanese arguably got more out of the Kaga than the Germans could have.

U-Boats have lost the Battle of the Atlantic, so is pointless to build more.

U-boats were their best bet to win the battle of the Atlantic. But they needed next generation u-boats deployed in 1943 to stand a chance against the Allies introducing improved ASW technology and doctrine.

 

[EwenS]

Wouldn't have put down an ounce of Steel for G.Z. Make a deal with Japan and buy Kaga from Japan in 1936, and license to build Kates

That is a non-starter.

At the beginning of 1936 Japan has Hosho & Kaga in commission and needed for support operations in China, Akagi under reconstruction (until 1938), Ryujo in refit to improve her seaworthiness (until mid-1936) and Soryu under construction with Hiryu to be laid down in July. She has no shipyard capacity to build a replacement for Kaga at that point.

The B5N was only in development in 1936 (ff Jan 1937 with combat ready models appearing in 1938). It had largely been superseded by the improved B5N-2 (ff Dec 1939) model by PH, and it's successor the B6N Jill (ff Mar 1941) was already in flight test).

 

[Zmauky]

The best strategy regarding naval aviation ... fleet in being as well as B & T.
So, as soon as AGNA is signed, take something under 10 kt (it is not subject to the contract? at least in WNT/LNC they are not) so that they can play and try it out and around '37-'38-'39 start building 2x carriers under 20 kt (before 4 British "I" they have - had ? free approx. 36 kt available). They probably wouldn't be ready for Norway, but it doesn't really matter, question is how many ships RN would have to keep in home waters.
And just maybe the small tonnage would prevent ideas about heavy artillery and a (too) complicated catapult system (at least for defence - the trolley system is British).
Of course, I support independent naval aviation (including land-based ones).

 

[EwenS]

So, as soon as AGNA is signed, ..... start building 2x carriers under 20 kt (before 4 British "I" they have - had ? free approx. 36 kt available). They probably wouldn't be ready for Norway, but it doesn't really matter, question is how many ships RN would have to keep in home waters.

Broadly that is what the KM intended to do.

The tonnage available to them under AGNA was 38,500 tons or so (standard displacement as defined in the 1922 Washington Naval Treaty, not full load as quoted in Wiki). GZ was initially planned at 19,700 tons standard (just over half the available tonnage) but changes to the design saw that grow to about 22,000 tons standard (approx 31,000 tons full load) during construction. That would have allowed construction of a second ship within the limit available to them.

The keel of the second ship, the unnamed Flugzeugtrager B was laid down 10 May 1938. In mid-Sept 1939, when she was complete to her armoured deck, work was stopped and the hull scrapped from Feb 1940. Shipyard capacity didn't allow it to be laid down earlier without sacrificing something else.

 

[Thumpalumpacus]

I'm not sure that there's a clear answer whether it's better for land-based maritime aviation to be under the control of the navy or the air force in general. Probably the answer ends up being more a result of inter-service turf wars.

I think it's clearly better to have maritime patrol subordinated to the navy. It prevents turf wars and reduces the acquisition of inappropriate aircraft, not to mention keeps the chain-of-command simpler and therefore more responsive to exigency.

 

[Zmauky]

Yes, they just jumped over that school ship from '35-'36 (after AGNA) and with the first GZ project went over half the tonnage. So instead of keeping the given tonnage (which was never the case) they added half more.