Negotiated Away:
Japan’s Lost Battleships
By Mike Bennighof, Ph.D.
February 2020

In late 1921, delegates from nine nations gathered in Washington for a series of conferences. Three treaties emerged: the Nine-Power Treaty affirming China’s territorial integrity and independence, the Four-Power Treaty respecting colonial possessions in the Pacific region, and the Five-Power Treaty, usually called the Washington Naval Treaty.

The Five-Power Treaty resulted in wholesale scrapping of older warships and placed limits on the size and number of newly built ships. American, British, Japanese, French and Italian battleship fleets would be limited to a ratio of 5:5:3:1.75:1.75, respectively. Most of the signatories were very glad to escape the crushing financial burden of the post-war naval arms race. The Japanese also sought limits, but left Washington extremely unhappy with the bargain they felt had been forced upon them.

Japanese unhappiness with the unequal treaty led to resentment within the military and government that in turn led to the Great Pacific War. The Japanese felt they had been rolled, and though they did not know it they did have good reason to feel that way. American intelligence analysts had intercepted the instructions sent from Tokyo to the Japanese delegation. While the Japanese held out for a 5:5:4 ratio, they had been told they could go as low as 5:5:3 if it meant the difference between having an agreement and leaving Washington empty-handed. Most other delegations were willing to accept the suggested Japanese level, including the Americans - at least before their code-breakers tipped them off.

Delegates hammer out the first treaty to actually require signatories to destroy weapons.


Had the Japanese obtained their desired 5:5:4 number, their allowable tonnage would have risen from 315,000 to 420,000. That would have preserved both units of the new Kaga class and one of the Amagi class battle cruisers, added to the six battleships and four battle cruisers retained at the 315,000-ton level. It's also possible, though probably less likely, that the Japanese would have chosen to keep one Kaga and two battle cruisers. In either combination, these three ships would have been the most powerful in the Imperial Japanese Navy, providing a much greater increase to the battle line's fighting power than simple tonnage might suggest.

Kaga and Tosa would have been 39,000-ton battleships, improved versions of the two-ship Nagato class. They carried ten 16-inch guns, and like Nagato were designed to make 26.5 knots using the very successful hull form of previous class — a much greater speed than foreign battleships of the time, and greater than any foreign observers credited until the late 1930's. But like Nagato, it's unlikely they would have played a major role in the Great Pacific War. Nagato and her sister Mutsu took part in the May-June 1942 Midway operation, remaining hundreds of miles astern of the carrier force, but otherwise did not leave the Home Islands before Mutsu exploded at anchor in June 1943. Nagato finally ventured forward that August, sailing for Truk and becoming somewhat more active there, participating in two sorties attempting to intercept American carrier raids. Not until mid-1944 did the battleship begin to see more action, deploying for the battles in and around the Philippines including the action off Samar. Nagato survived the Philippine battles only to be relegated to coastal defense in Japan that January; by June her anti-aircraft guns had been moved ashore replaced with potted plants to complete her camouflage as she became a floating barracks. American sailors took possession in late August.

Japanese sea power. From front: Nagato, Kirishima, Ise, Hyuga.


Two more similar battleships, despite their greater size and firepower, surely wouldn't have been treated any differently. Kaga and Tosa would either have perished in the Philippines under massive American air attacks, or survived to be expended as targets for American atomic bomb tests.

In contrast, one or two Amagi-class battle cruisers could have had a larger but still questionable impact on the course of the Great Pacific War. Japanese practice usually placed the four Kongo-class battle cruisers with the carrier groups as fast escorts, and they were flung into the fighting for Guadalcanal as part of the cruiser forces. Hiei was damaged in surface combat and finished off by air attacks. Kirishima was sunk in a night action off Guadalcanal two days later by the American battleship Washington.

Amagi weighed in half again as large as Kongo, with ten 16-inch/50-caliber main guns as opposed to the eight 14-inch guns of Kongo, thicker armor and a higher original speed. The four Kongo-class ships were considerably improved in the 1930's, with improvements to their protection scheme and new machinery yielding a 30-knot speed that matched Amagi's design speed. Amagi (and Akagi, if a second ship survived) would likely have undergone similar reconstruction, at least to their armor protection.

Amagi as planned.


The Kongo-class battle cruiser Hiei was lost due to a single 8-inch hit from the American cruiser San Francisco, which slowed her enough to make her easy prey for American pilots once day broke. Amagi probably would have shrugged off the same hit and survived. Kirishima's case is much different.

While they had a front-line role in Japanese carrier operations, during peacetime the four Kongo-class battle cruisers trained with the battleships rather than the cruiser forces. They did not undertake the same rigorous night combat practice as cruiser and destroyer crews, and when they were committed to surface action in the Solomons they fought the way they had trained. In her fateful encounter off Guadalcanal, Kirishima fired 117 rounds at the American battleship South Dakota, managing to hit her just once despite the nearly point-blank range of 5,500 yards. The cruisers Takao and Atago, in contrast, hit South Dakota 17 times with their 8-inch guns and blew away most of her unarmored upper works, rendering the big ship unable to continue the fight.

With the aid of radar and crack gun crews, Washington opened fire on Kirishima at 8,400 yards. Kirishima took 18 hits from 16-inch shells, most of them in the span of just five minutes (the damage came so quickly that the Japanese believed she had been hit nine times, the Americans, eight). Catastrophic flooding caused her to capsize and sink within two hours.

Battleship Tosa, Kaga's sister ship, after launch.


Amagi's greater size and staying power, plus larger guns and more of them, might not have made much difference. Japanese gunners aboard Kirishima fared poorly, and there's no reason to think Amagi's would have done any better. The massive damage inflicted by Washington would have overwhelmed Amagi just as easily; the super-battleship Yamato (even the space-cruiser version) might not have stood up to that kind of punishment.

Japan's problems lay in the use of her battleships and the training of their crews. A few more of the big ships would have given the Imperial Navy more options if they were willing to use them, but these would be meaningless if the ships were simply held back for a decisive battle that could only take place after Japan's defeat had become inevitable.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and award-winning journalist, he has published over 100 books, games and articles on historical subjects. He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold.