WW2 Japanese Naval Doctrine, what exactly was it?

by [deleted]

I watch a lot of documentaries on the second World War, but one thing that they seem to universally disagree on is WHAT, exactly​, the Japanese Naval Doctrine was at all. Maybe this isn't a great question, but I'm simply confused. I have heard that they emphasized big gun battleships and cruiser, or they emphasized carriers, or they even emphasized night torpedo attacks from destroyers. So if somebody could clarify, that would be great!

Avatar_exADV

Almost all of those things are correct all at once!

Japanese naval doctrine was extremely focused on the Decisive Battle. The idea was articulated by Mahan (an American admiral) and the substance was basically that defeating the enemy's fleet was the most important aspect of naval warfare; yes, convoy protection and blockade and troop landings, but none of that mattered if you couldn't actually beat the opponent's main strength (and was a lot easier if you DID beat their main strength).

The Battle of Tsushima, which was the climax of the Russo-Japanese War, drove this point home with the Japanese leadership; the Japanese fleet engaged the Russian fleet and effectively annihilated it, removing Russia's ability (or at least their will) to continue the war.

The Japanese thus needed to figure out a way to successfully prosecute the Decisive Battle in the face of American opposition (the US being the Navy's assumed opponent in any such encounter). This was very tricky to plan, as the US had a significant advantage in ships due to the Washington Treaty (and after the treaty was abandoned, due to being a lot bigger and wealthier than Japan). At the time, it was appreciated that a numeric advantage in battleships led to a big advantage in combat - six ships versus six ships would be a nasty brawl, but twelve versus six would win much more easily and with a lot less damage. So how did they plan to win?

The attack was planned to begin the night before the general fleet engagement. Various Japanese destroyer groups, each with a light cruiser as a flagship, would approach from various directions in the dark and execute what was hoped to be a massive simultaneous torpedo attack. The idea was that this would be unexpected as such operations are -hideously- difficult to pull off, and the Japanese trained their ships relentlessly to be able to do it; this training ended up paying off in the waters off Guadalcanal on more than one occasion.

Beyond the night attack, the Japanese planned to deliver more firepower, with better aim. Their ships had a very notable emphasis on armament and speed, with less emphasis on armor and seaworthiness; more than one class of Japanese vessel had to be redesigned due to being too top-heavy or not structurally sound enough to weather heavy storms. The Japanese had several heavy cruisers that were in excess of the Washington Treaty's 10,000-ton limit (and not by a little, in some cases). They hoped to out-range and out-gun the US battle line, to get hits from beyond the effective range of US ships and to get more hits at equivalent ranges. The super-battleships were another outgrowth of this kind of thinking; if the Japanese could not have more ships, at least they could have larger ones with better armament.

Ironically, the carrier groups were not expected to contribute to this much more than performing scouting duties and interfering with US carrier operations. The Japanese did effectively develop carrier doctrine to a high degree, but it wasn't something that was integrated clearly into the Decisive Battle thinking in the Japanese leadership. Likewise, submarines weren't expected to do much more than provide picket lines and maybe pick off a few ships.

It probably wouldn't have worked. The Japanese plans required a lot of coordination and generally rested on the assumption that the Americans would come in fat, dumb, and happy - but the US navy had its own defensive doctrines. The Japanese advantages in training, superior night optics, etc., were almost completely obviated by US developments in radar.

Beyond that, it assumed that the US would also seek a decisive battle; it's been argued that the very success of Pearl Harbor made that impossible by sinking a large portion of the US battle line, and forcing the US to take a more round-about approach focused on carrier warfare and commerce interdiction.

If you're interested in the topic of the pre-WW2 Japanese navy, I definitely recommend reading Kaigun by Evans and Peattie, which goes into the various topics of naval construction, design, leadership, and doctrine in great and enjoyable detail.

thefourthmaninaboat

Japanese naval doctrine in this period is generally classified as a 'decisive battle' doctrine. The primary aim for the Imperial Japanese Navy (IJN) was to fight a single battle which would completely destroy the opposition's ability to fight a war at sea. This was informed by the experiences of the Russo-Japanese War, where such a battle was fought at Tsushima. The theorised decisive battle was to be a complex, combined arms battle, with roles for all three classes of ships you mention, as well as for land-based aircraft. Carriers and aircraft were to open the battle, with three key objectives; destroy enemy carriers, protect the fleet against enemy air attacks, and attrit the enemy battlefleet. This would be further damaged by a nighttime torpedo engagement, in which the Japanese screen would use the cover of night and the range of their torpedoes to compensate for their comparable fragility. The battleline, so weakened, would then be easy prey for its Japanese counterparts. This was a capable, but complex doctrine with two major points of failure. Firstly, it created a brittle force - as it would only have to fight a single battle, there was no need to train reinforcements and replacements. However, losses to aircraft maintainers at Midway and to aircrew in the Solomons would prove this wrong in real-world conditions. Secondly, it would encourage IJN commanders to create complex plans. These were hugely vulnerable to defeats in detail, as at Midway and Leyte Gulf.