Japan's Semi-Dreadnoughts
By Mike Bennighof, Ph.D.
August 2021

Victory over Russia in 1905 brought the Japanese Empire into the ranks of modern powers, the only such nation outside the “white” world of Europe and North America. While the alliance with Britain and the twin victories of Tsushima and the Yellow Sea confirmed Japanese power, they also meant that Japan had a new status to defend. And after 1906, that status was measured in the number of dreadnought battleships a navy commanded.

The Russo-Japanese War gave the Japanese Navy some hard-won lessons and a great deal of new material rapidly becoming obsolescent. When war seemed imminent the Japanese quickly bought two armored cruisers under construction in Italy for Argentina. Two battleships were under construction in Britain, and a war emergency program authorized two more battleships, along with a number of cruisers and a large selection of light craft. And in the course of the war, five Russian battleships — several of them badly damaged — fell into Japanese hands as well.

The two British-built ships, Kashima and Katori, arrived in June, 1906. Their design was very similar to the contemporary British King Edward VII class, but with Armstrong 10-inch guns in their "corner" positions in place of the 9.2-inch in their British near-sisters. Each carried a mixed armament of four 12-inch guns, four 10-inch guns and a dozen six-inch guns.

Satsuma as completed.

Training exercises showed that at longer ranges, it became difficult to separate the splashes of 12-inch and 10-inch shells. While traditionalists continued to emphasize close action in the Nelson fashion, others foresaw that surface battles would be fought at the ever-greater ranges permitted by modern guns and optics. And eventually wartime experience would show mixed armament to be a mistake — big guns determined the outcome of battleship actions, and the higher rate of fire produced by smaller tubes did not compensate. But even before the fighting commenced, the Navy told its designers to come up with a ship carrying a uniform armament of 12-inch guns for the next generation of battleships.

The new class of two ships authorized in the war emergency program would be built in Japanese yards, though with considerable material imported from British and American manufacturers (over 60 percent of the total). The initial design called for eight 12-inch guns in four twin turrets, arranged in pairs fore-and-aft but on the same deck level. That prevented the second turret in each pair from firing directly ahead or astern.

Japanese thought had been merging the roles of the battleship and the armored cruiser, and this design reflected that trend. She had belt armor of only seven inches, the same as the armored cruiser Tsukuba then also being designed as part of the same program. Tsukuba was also a hybrid design, with a battleship's main armament (four 12-inch guns) and a cruiser's speed and protection. The new battleship design needed to be substantially better protected than an armored cruiser, and the Navy rejected the proposal.

Now facing hard deadlines, the designers drafted a ship based on an enlarged Tsukuba with heavier armament and better protection. In profile she looked very much like the cruiser, with a flush deck where Tsukuba's was broken. She would have a dozen 12-inch guns, with twin turrets four and aft and in each "wing" position, and single turrets at the "corners." The Navy accepted the design and placed their orders, making Japan the first nation to order a dreadnought-type battleship.

Satsuma as designed and accepted.

Both ships would be built at Japanese Naval Yards. Satsuma was laid down at Yokosuka in May 1905, two weeks before the climactic Battle of Tsushima and five months before Britain's Dreadnought. Wartime delays had kept Tsukuba on the slipway at Kure, and the second battleship, Aki, could not be laid down until the cruiser had been launched. Construction finally commenced in April 1906.

Problems cropped up almost immediately. The delays in starting Aki caused the inevitable tinkering — both the Navy and her designers sought to make improvements while they waited for the slipway to clear. The Navy wanted to test turbine propulsion in a large warship, and ordered a set from Curtiss in the United States. The design team upgraded the secondary armament from the dozen 4.7-inch guns in Satsuma to eight 6-inch guns for Aki. Because of the change in machinery, Aki had three funnels where her sister had two.

Japan could not yet produce heavy naval guns, and while the sisters had been designed and laid down, Britain started a naval revolution with the launch of HMS Dreadnought in February 1906 and by laying down the equally innovative battle cruiser Inflexible a month later. Three sisters followed Dreadnought within a year, and two more battle cruisers.

For the previous decade, a typical British class of four battleships would have required sixteen 12-inch guns. Dreadnought alone carried 10. The armored cruisers that preceded the new battle cruisers carried no big guns; each of the new ships had eight. Suddenly the Royal Navy's purchase of 12-inch guns for its naval building program leapt fourfold, from 16 to 64. And Brazil had already placed orders for three battleships requiring another 36 big guns.

Only two private firms manufactured heavy guns in Britain, Armstrong's and Vickers. They had been colluding for years to obtain foreign contracts and now used their duopoly to force prices to skyrocket. Armstrong's may also have carried a grudge against the Japanese for building their new ships in their own yards after a long run of orders from the firm's shipbuilding division.

The American-built Russian battleship Retvisan, later the Japanese Hizen.

For reasons of graft and prestige, the Imperial Navy had already committed huge sums to rebuilding the captured Russian battleships. These five ships doubled the Japanese battle line, but were by no means modern fighting units and would soon be rendered totally obsolescent. The government considered it a very telling sign to have the former Russian ships under the Japanese flag, and pressed the Navy to give the project priority. All the Russian ships would receive the new Japanese-designed and -built Miyabara boiler system, and the order represented a massive cash influx to the new industry. Too many jobs, and too much profit, rested on the rebuilding project.

All the ex-Russian ships required new main armament, totalling twenty 12-inch guns. Facing financial ruin after their war with Russia, and with the Americans demanding cash up front for Aki's machinery, the Japanese could not afford forty-four 12-inch guns — 24 for their two new battleships and 20 more for the Russian prizes.

But Armstrong’s offered a compromise solution. The firm had begun turning out a large number of 10-inch guns on the basis of an order from Brazil for three small battleships each carrying a dozen of the weapons. And when Sir John Fisher was elevated to First Lord of the Admiralty, they believed that his enthusiasm for the 10-inch gun’s rapid fire would lead to its adoption in the new generation of battleships. That didn’t happen, and the cannon foundry was left with a large number of guns without a customer, and offered them to the Japanese at a bargain price.

Grudgingly, the Japanese accepted. They assigned the 12-inch guns they did manage to buy to the ex-Russian ships, and re-cast the design of Satsuma and Aki around the 10-inch guns. The corner and wing turrets would each be replaced with a twin 10-inch turret, giving each ship a battery of four 12-inch guns and a dozen 10-inch guns. This added more construction delays to the two “semi-dreadnoughts,” and they had been surpassed by most other nations when they entered service, Satsuma in March 1910 and Aki a full year later.

Aki with her three funnels.

Aki proved almost two knots faster than her sister, proving turbine technology to the Imperial Navy. But neither ship was very satisfactory, outdated even as they made their first cruises. They saw very little service during the First World War, cruising offshore during the deployment to capture Tsingtao from the Germans. Satsuma went to Rabaul in October 1914 as flagship of the Second South Sea Squadron assembled to search for the German East Asia Cruiser Squadron but no action resulted.

The Japanese faced impossible choices: to maintain their status, they had to build impressive new warships, but the war that brought them this status had also destroyed their finances. The British move to all-big-gun ships could not have come at a worse time for Japan, but it was inevitable. As anyone who has run a game company knows, circumstances beyond one's control often seem to conspire to strike at the worst possible time, and so it was for the Japanese and their two semi-dreadnoughts. By compromising and spreading the big guns over the Russian prizes and the new ships, the Imperial Navy ended up with seven ships of limited fighting power instead of two good ones and five piles of scrap steel. The money spent at a time when Japan could not afford it turned out to be largely wasted. Both semi-dreadnoughts remained in service through the First World War and were used as targets in 1924 — officially to meet the requirements of the Washington Naval Treaty, but they had been written off in practical terms years before.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and NASA Journalist in Space finalist, he has published countless books, games and articles on historical subjects. He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold.


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