Had all four Yamato-class battleships been converted into aircraft carriers, like the Shinano, the Pacific Theater of World War II could have seen significant changes, particularly in terms of naval tactics, air power projection, and the balance of naval strength between Japan and the United States. Here's how this scenario might have affected the war:
1. Increased Japanese Carrier Strength
The Yamato-class battleships—Yamato, Musashi, Shinano, and the incomplete Yamato-class sister ship (known as No. 111 or a potential second Musashi)—were the largest battleships ever built, designed to be formidable in direct naval engagements. Converting these giant ships into carriers would have dramatically increased Japan's carrier strength. With the loss of Japan's carriers during the Battle of Midway (like Akagi, Kaga, Soryu, and Hiryu), the Imperial Navy struggled to maintain air superiority over the vast Pacific.
Carrier Conversion Advantages: A fully operational fleet with four Yamato-class carriers would have significantly boosted Japan's ability to launch air strikes, defend its fleet, and carry out offensive operations. These converted ships, given their large size and capability to carry significant air wings, could have carried anywhere from 60 to 100 aircraft each, providing Japan with a much larger and more powerful carrier fleet.
Potential Impact on Carrier Battles: The presence of these large carriers could have provided the Japanese Navy with a stronger counterforce to the U.S. carriers. At critical moments like Midway, this extra air power could have allowed Japan to retaliate more effectively, potentially altering the course of the battle.
2. Shift in Naval Tactics and Strategy
The Yamato-class battleships were originally designed to fight in a large-scale surface engagement. Their conversion into aircraft carriers would have necessitated a shift in Japanese naval tactics, moving from traditional battleship-centric strategies to more carrier-based tactics, similar to the U.S. Navy’s approach. This shift would have:
Requiring New Training: The Japanese Navy would have needed to train more air crews and support personnel, as well as adjust their naval doctrine to better integrate the carriers into their fleet. A stronger emphasis on carrier aviation would have had a profound impact on how Japan approached both offensive and defensive operations.
Air Superiority Focus: With more carriers, Japan could have had more aircraft to contest U.S. air superiority. Battles like the Battle of the Philippine Sea and the Battle of Leyte Gulf, where U.S. forces decisively destroyed Japanese carrier air groups, could have been different if Japan had maintained more capable carriers.
3. Prolonged Naval Engagements and Delayed U.S. Victory
If the Yamato-class ships had been converted to carriers, Japan’s overall naval strength could have been far more formidable. The U.S. Navy would have faced a much stronger fleet and potentially delayed victories in key battles like Midway and Coral Sea, both of which were pivotal in halting Japanese expansion.
Longer War in the Pacific: The presence of multiple powerful carriers could have allowed Japan to maintain a more significant naval presence in the Pacific, making U.S. victories in battles like Leyte Gulf and Okinawa more costly and prolonged.
Potential Strategic Shift: With more carriers, Japan could have focused on more decisive strikes, perhaps even targeting the U.S. Pacific Fleet more effectively. This could have meant slower American progress across the Pacific, especially in terms of island-hopping campaigns.
4. Resource Strain and Strategic Challenges
On the flip side, converting the Yamato-class battleships into aircraft carriers would have placed an enormous strain on Japan’s already limited resources. While the larger carriers would have given Japan increased capabilities, maintaining them—along with the aircraft, personnel, and logistical support—would have been challenging given the resource shortages and industrial limitations Japan faced throughout the war. Additionally:
Vulnerability of the Yamato-class Conversion: The Yamato-class battleships were already huge, making them vulnerable to air attack and torpedoes. Converting them into carriers wouldn’t have mitigated these vulnerabilities, and the ships would have still been prime targets for U.S. bombers and submarines.
Allied Countermeasures: The U.S. had already adapted to carrier warfare by the time the Yamato-class ships were converted. The U.S. Navy would likely have found ways to counter the increased number of Japanese carriers, whether through improved radar, submarine warfare, or advanced bombing tactics like those used to sink the Shinano.
5. The Effect on Post-War Naval Developments
If the Yamato-class ships had been converted to carriers, it could have delayed the emergence of the aircraft carrier as the dominant force in naval warfare. The U.S. Navy’s aircraft carrier superiority, which was critical in World War II, might have faced more competition for longer, possibly influencing the post-war naval arms race and military strategies of both countries.