Comments by "Sar Jim" (@sarjim4381) on "IJN Fubuki - Guide 165" video.

The strange thing about the IJN and its use of AA guns was they had one of the best heavy AA guns, the Type 98 100 mm gun from 1940 onwards, but they armed only a few classes ships by 1945, the majority being diverted to land AA use. Prewar, they had purchased British 2 pdr pom pom guns in several batches, with at least 500 examples being on hand by 1935. These were used in single and twin mounts. The Japanese considered them only useful in smaller ships like subchasers and minesweepers after 1935, judging their 25 mm Hotchkiss design to be superior. They had also purchased examples of German 20 mm and 37 mm guns as well as Oerlikon 20 mm types. They captured at least one hundred fifty 40 mm Bofors guns after the Fall of Singapore. Even more of a windfall, they had captured another sixteen examples of the Dutch 40 mm, the most fully developed Bofors guns in the world in 1940. It's not a matter of the Japanese only having 25 mm guns, it was a matter of the IJNs laser focus on torpedoes and torpedo warfare. The Japanese economy had been shattered by the Great Depression and the military spending required by the war in China. Given their limited resources, the IJN rightly decided that having the world's best torpedo, among the best torpedo mounts, and large destroyers and cruisers carrying lots of the Type 93 torpedoes was a war winning strategy. The results of such thinking in 1942 through early 1943 showed that they weren't wrong, especially combined with the IJN's almost obsessive training in night fighting. However, that was only true for surface warfare. Even though the Japanese had been among the first navies to understand the theory and use of aircraft carrier, they developed very little understanding of how to defend against the enemy's aircraft. Their limited resources didn't allow them to develop three or four different types of AA weapons, so the decision was made to mass produce the type they already had and understood how to produce. After 1942, they knew the 25 mm gun was marginal at best and started working on reverse engineering the Bofors and Oerlikon guns. By 1944, their industrial infrastructure was being cut to ribbons by US bombardments, the merchant fleet they needed to bring in steel and other critical materials was increasingly on the bottom of the sea, and they were running out of time. From postwar US reports, they had working prototypes of Bofors and Oerlikon guns ready for production, but not until June, 1945, and they didn't have the material needed for mass production in any case. It was the IJN's narrow vision of how naval warfare would develop in what became WWII that left them without an effective AA gun, not they couldn't have developed one.
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@bkjeong4302 The real plan was to develop such a strong defensive line that the Americans couldn't break through without being destroyed. It wasn't just carrier aircraft that they had to defend against. From Guadalcanal forward, they had defend against our occupying islands that became unsinkable carriers. They just didn't have the fleet or resources large enough to prevent this. Every island we seized became an airbase that attacked the next island in our plan while striking at Japanese shipping. AA gunnery on ships and land became more and more important, yet the Japanese didn't seem to pay it much attention. The fighting between the Army and Navy over strategy and resources became almost as important as fighting the Allies. Regardless of how many of our carriers they could sink after the Coral Sea, we could build them faster than they could sink them. It seemed as if only Yamamoto realized what dire straits the Japanese were in by 1943, but even he couldn't convince the General Staff of the necessity of a defensive war after the disaster at Midway.
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@bkjeong4302 YOu're right that the Japanese were focused on the "decisive attack". I don't think that was ever their exclusive plan for dealing with enemy air attacks. If it ever was, that plan was dashed after Midway. Nevertheless, the Army and Navy continued to fight about who'd develop things like radar first. There was no serious attempt to reverse engineer the Bofors gun until 1944. Rather than evacuating men from isolated islands for use in strategically more defensive areas, they continued fruitless attempts to resupply those troops, apparently believing that the US would somehow double back and attack them. By the time a decision had been made to withdraw them, it was too late, and many of those poor guys slowly starved to death. They didn't put serious efforts into developing more powerful aero motors for fighters than the one that already existed in the Zero because of the "decisive battle" delusion. With the appearance of the Hellcat and, worse, the Corvair, it was a mad scramble to develop in 1943/44 what should have been done in 1940, when they still had resources and manpower to do it. The Japanese plan for the "decisive battle" was not the destruction of the US fleet, just to cause enough damage and deaths that US would sue for an armistice. Yamamoto knew the only hope for such an event was a series of bold strikes early on. If the damage to the US fleet in 1942 wasn't enough to bring America to its knees, he knew only a long, protracted war would have an chance for the US suing for peace. He had been advocating for a defensive plan since before Pearl Harbor but he was generally ignored. The IJN never seemed to understand that unrestricted submarine warfare against US merchant shipping was the only hope for weakening the fleet and the troops ashore. By the time even the Army and General Staff were convinced that no "decisive battle", or at least not one in favor of the IJN, was going to happen and defense was the only option, it was far too late for any defensive plan to work.
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