Satsuma-class battleship

Line drawing of the battleship Satsuma from Brassey's Naval Annual 1912. Aki similar, but three funnels.

The Satsuma class was ordered in late 1904 under the 1904 War Naval Supplementary Program during the Russo-Japanese War.[1] Unlike the previous Katori-class pre-dreadnought battleships, they were the first battleships ordered from Japanese shipyards, although the first ship in the class, Satsuma, used many imported components.[2]

They were originally intended to mount a dozen 12-inch (305 mm) gun in four twin and four single-gun turrets, but the combination of a shortage of Japanese-built 12-inch guns[3] and their additional expense[2] caused the ships to be redesigned to carry four 12-inch and twelve 10-inch (254 mm) guns, all in twin-gun turrets.[3] The intended armament of these ships, laid down before HMS Dreadnought, would have made them the first "all big-gun" battleships in the world had they been completed to their original design.[4]

Probably reflecting extensive British technical assistance, the Satsuma-class ships greatly resembled an enlarged version of the British Lord Nelson class with the single-gun amidships intermediate turrets replaced by twin-gun turrets.[4] With their heavy intermediate armament, the ships were considered to be semi-dreadnoughts, a transitional stage between pre-dreadnoughts with their light intermediate armament and dreadnoughts solely equipped with large guns.[5]

The construction of Aki was delayed since she could not be laid down until the slipway occupied by the armored cruiser Tsukuba was freed by that ship's launching. The IJN took the opportunity provided by the delay to modify the ship to accommodate steam turbines and various other changes that generally increased her size. The changes were great enough that Aki is generally considered a half sister to Satsuma.[3] The crew ranged from 800 to 940 officers and enlisted men.[5]

Satsuma had an overall length of 482 feet (146.9 m), a beam of 83.5 feet (25.5 m), and a normal draft of 27.5 feet (8.4 m). She displaced 19,372 long tons (19,683 t) at normal load. Aki was 492 feet (150 m) long overall, had a beam of 83.6 feet (25.5 m), and the same draft as her half-sister. She displaced 20,100 long tons (20,400 t) at normal load.[5]

The completion of the British battleship Dreadnought with her all big-gun-armament and steam turbines in 1906 meant that these ships were obsolete even before they were completed. The IJN recognized that fact when it drew up the first iteration of its Eight-Eight Fleet building plan for eight first-class battleships and eight battlecruisers in 1910 and did not include them.[16]

Aki was refitting at Kure and Satsuma was assigned to the 1st Battleship Squadron when World War I began in August 1914.[4] The latter served as Rear Admiral Tatsuo Matsumura's flagship in the Second South Seas Squadron as it seized the German possessions of the Caroline and the Palau Islands in October 1914.[17] Satsuma rejoined the 1st Battleship Squadron in 1915, was refitted at Sasebo Naval Arsenal in 1916 and served with the 1st Squadron for the rest of the war. Aki was also assigned to the 1st Squadron upon the completion of her refit and remained with it until she was transferred to the 2nd Battleship Squadron in 1918.[4]

In the years immediately following the end of the war, the United States, Britain, and Japan all launched huge naval construction programs. All three countries decided that a new naval arms race would be ill-advised, and so convened the Washington Naval Conference to discuss arms limitations, which produced the Washington Naval Treaty, signed in February 1922.[18] Japan was well over the tonnage limits and all of her obsolete predreadnought and semi-dreadnought battleships had to be disposed of by the end of 1924.[19] Both ships were disarmed at Yokosuka in 1922, stricken from the Navy List during 1923 and converted into target ships. Aki was sunk by the battlecruiser Kongō and the battleship Hyūga in Tokyo Bay on 2 September 1924; Satsuma was sunk by the battleships Nagato and Mutsu five days later in the same area.[7]

• Evans, David & Peattie, Mark R. (1997). Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887–1941. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-192-7.
• Friedman, Norman (2011). Naval Weapons of World War One. Barnsley, South Yorkshire, UK: Seaforth. ISBN 978-1-84832-100-7.
• Gardiner, Robert & Gray, Randal, eds. (1985). Conway's All the World's Fighting Ships 1906–1921. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-907-3.
• Itani, Jiro; Lengerer, Hans & Rehm-Takahara, Tomoko (1992). "Japan's Proto-Battlecruisers: The Tsukuba and Kurama Classes". In Gardiner, Robert (ed.). Warship 1992. London: Conway Maritime Press. ISBN 0-85177-603-5.
• Jentschura, Hansgeorg; Jung, Dieter & Mickel, Peter (1977). Warships of the Imperial Japanese Navy, 1869–1945. Annapolis, Maryland: United States Naval Institute. ISBN 0-87021-893-X.
• Lengerer, Hans & Ahlberg, Lars (2019). Capital Ships of the Imperial Japanese Navy 1868–1945: Ironclads, Battleships and Battle Cruisers: An Outline History of Their Design, Construction and Operations. Vol. I: Armourclad Fusō to Kongō Class Battle Cruisers. Zagreb, Croatia: Despot Infinitus. ISBN 978-953-8218-26-2.
• Peattie, Mark R. (1988). Nan'yo: The Rise and Fall of the Japanese in Micronesia 1885–1945. Pacific Island Monograph Series. Vol. 4. Honolulu, Hawaii: University of Hawaii Press. ISBN 0-82481480-0.
• Preston, Antony (1972). Battleships of World War I: An Illustrated Encyclopedia of the Battleships of All Nations 1914–1918. New York: Galahad Books. ISBN 0-88365-300-1.
• Silverstone, Paul H. (1984). Directory of the World's Capital Ships. New York: Hippocrene Books. ISBN 0-88254-979-0.

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• Materials of the Imperial Japanese Navy