After forcing the emperor to abandon the delusion of restarting battleship construction, Yamamoto went on to explain the other two major shortcomings of battleships, "Secondly, the materials and workmanship requirements of battleships are much higher than those of aircraft carriers. When there is no way, aircraft carriers can even be built using the materials and craftsmanship of merchant ships to reduce costs, but it is impossible for battleships to do that, let alone be attacked by the enemy, and even fire a cannon themselves will cause the structure to disintegrate. This determines that the construction cost and maintenance cost of aircraft carriers are much lower than that of battleships, and the cost of aircraft carriers is at least 30% lower than that of battleships with the same displacement, and if we take into account the special national conditions of Japan's rare metals all imported, this gap is far greater than it seems, and compared with the cost, the gap between the maintenance costs of the two will only be greater."

"And the maintenance of the battleship is not only a matter of money, the consumption of time is the most fatal, once the battleship is damaged, it can be a month or two, or more than half a year or even longer, and the repair time is much longer than that of an aircraft carrier. Moreover, the battleship seems to be indestructible, but the protection of non-key parts is still very weak, and injuries in those places, although they generally do not lead to the sinking of the warship, will seriously affect its combat effectiveness, and the time required for repair is not short at all. Moreover, the probability of failure of the battleship itself is also greater than that of the aircraft carrier, and unlike most of the failures of the aircraft carrier, which can be solved only by the maintenance personnel on the ship, the battleship basically has to go back to the shipyard for maintenance. What's more, even if there were no injuries and no breakdowns, the frequency and time required for routine maintenance of battleships would be greater than that of aircraft carriers," Yamamoto 56 said in a rare way. Finally let Chongren rest the idea of restarting the battleship construction jihua, no way, you must know that Chongren also grew up under the influence of the "giant ship cannon doctrine", if you don't pay attention to it, the vision of your childhood will affect the decision-making

As for the issue of air defense of the fleet, Yamamoto Isoroku also put forward his plan, that is, to build a large number of light warships specially used for air defense, which is more practical than building battleships to strengthen the air defense of aircraft carrier formations, and the first batch of four Akizuki-class air defense destroyers and their improved versions that have been completed and put into service have therefore received greater attention from the Japanese Navy.

The Akizuki-class destroyer was historically one of the best anti-aircraft destroyers of World War II, and this time and space was due to the fact that Japan acquired the gunning radar and proximity fuse jishu from the Germans. and because of the relationship between being sheltered and supported by the United States. The Erikon 20mm anti-aircraft gun and the more classic Bofors 40mm anti-aircraft gun were purchased from Switzerland and Sweden respectively, and copied and improved them (Note 1), and the actual air defense capability was several times higher than in history, thus becoming the undisputed best air defense destroyer in Shijie.

In addition, due to the fact that the European war broke out more than a year later than in history. Japan received more jishu transferred by Germany. Among them, the Japanese Type 105mm anti-aircraft gun, which was copied from the German Navy's 105mm anti-aircraft gun, was slightly stronger in performance and power than the Type 98 100mm anti-aircraft gun originally selected by the Akizuki class. However, the production difficulty was much smaller, and the cost was lower, so it was natural to completely replace the Type 98 100mm anti-aircraft gun, which exceeded the requirements of Japan's industrial capacity. It was used on the first 4 warships of the Akizuki-class destroyers.

Compared with the original model, the improved Crescent-class destroyer of the Akizuki-class was in place in one step, and when it was built, it was replaced with this new anti-aircraft gun, and the details were more reasonable. In addition, they have also increased the bulbous bow design, and the ship type is also more narrow and long than the prototype Akizuki class, so that the maximum speed has been increased from 33 knots of the original model to 35 knots required by the original design, in addition, the hull has also been enlarged, the standard displacement has increased to more than 3200 tons, and the fuel that can be carried has also increased a lot, and its endurance has been further improved to 10000 nautical miles / 18 knots, which also meets the strict requirements put forward when the original design was made, and the anti-submarine weapons have also been enhanced. The Hedgehog Bomb Launcher, which is now popular in the navies of the Great Powers, is equipped with a drum depth charge that can only be dropped by driving to the opponent's submarine as originally designed, with only two depth charge chutes as originally designed, and the depth is very shallow. Its basic performance parameters are as follows:

Displacement: 3250 tons (benchmark) / 4200 tons (full load).

Main dimensions: 145.2 m (overall length) / 11.6 m (width) / 4.2 m (draft).

Power: 2 ship-based steam turbines, 3 ship-based heavy oil boilers, 52,000 horsepower.

Speed: 35 knots.

Endurance: 10,000 nm / 18 knots.

Firepower: 4 twin-mounted 105mm anti-aircraft guns; 6 twin-mounted Bofors 40mm anti-aircraft guns; 6 twin Erikon 20mm anti-aircraft guns; 12 single-mounted Erlikon 20mm anti-aircraft guns.

Torpedo: 1 quadruple Type 92 610mm torpedo tube, equipped with 8 610mm caliber Zero heavy marine oxygen torpedoes (that is, the Type 93 oxygen torpedo improved by the introduction of Chinese Jishu).

Deep Bombs: 2 Hedgehog Bomb Launchers, 2 Depth Charge Slides.

Crew: 280 people.

In addition, it is worth mentioning that Japan also learned the assembly line shipbuilding method from the United States and the modular shipbuilding method learned from Germany, although neither of them improved the performance of the Crescent-class destroyers, but because of the relationship between design and process simplification, the production difficulty of the Crescent-class destroyers plummeted, and the overall cost was reduced by more than 20%, and the construction speed was incredibly fast, from the beginning of construction to the completion of the service only 3 months to half a year (Note 2). And the prototype of the Akizuki-class, which is historically inferior to the Crescent-class destroyers, took a year and a half to two years to complete, and the speed of construction was accelerated by four or five times.

After the Crescent-class destroyers were highly valued by the Japanese Navy, in the second half of 1941 alone, Japan built 9 destroyers, and the total production of Akizuki-class destroyers in history was only 12. In the first half of the following year, the output of this type of destroyer reached an astonishing 18 destroyers, and in the second half of the year, 24 Crescent-class destroyers were completed, which not only completely made up for the huge losses of the Japanese Navy's auxiliary ships in the war of aggression against China, but also greatly enhanced the overall strength of the Japanese Navy compared with the beginning

Note 1: Because the increasingly influential Japanese Federation of Industry and Economics advocates large-scale mass production, Japan finally simplified the design of the process of these two anti-aircraft guns like the Americans in history, reducing production costs and increasing production speed, but due to the thin industrial foundation, the effect is still not comparable with that of the United States. It is also worth mentioning that due to the actual needs of the Japanese Navy, they designed a twin modification of the Erlikon 20mm anti-aircraft gun earlier than the Americans.

Note 2: The first batch of four Akizuki-class destroyers was built at a relatively slow pace due to their Shiyan nature and the fact that they were not designated as a production priority at that time, taking more than a year, while the first batch of Crescent-class destroyers took only half a year, and the second batch of large-scale production after that reached an astonishing speed of completion within a quarter. (To be continued......)