Satsuma - class battleship The was a pair of semi - dreadnought battleship s built for the Imperial Japanese Navy ( IJN ) in the first decade of the 20th century . They were the first battleships to be built in Japan and marked a transitional stage between the pre - dreadnought and true dreadnought designs . They saw no combat during World War I , although led a squadron that occupied several German colonies in the Pacific Ocean in 1914 . Both ships were disarmed and expended as targets in 1922 – 24 in accordance with the terms of the Washington Naval Treaty of 1922 . Background . The " Satsuma " class was ordered in late 1904 under the 1904 War Naval Supplementary Program during the Russo - Japanese War . Unlike the previous pre - dreadnought battleship s , they were the first battleships ordered from Japanese shipyards , although the first ship in the class , " Satsuma " , used a lot of imported components . They were originally intended to mount a dozen gun in four twin and four single - gun turret s , but the combination of a shortage of Japanese - built 12 - inch guns and their additional expense caused the ships to be redesigned to carry four 12 - inch and twelve guns , all in twin - gun turrets . The intended armament of these ships , laid down before , would have made them the first " all big - gun " battleships in the world had they been completed to their original design . Probably reflecting extensive British technical assistance , the " Satsuma " - class ships greatly resembled an enlarged version of the British with the single - gun amidships intermediate turrets replaced by twin - gun turrets . With their heavy intermediate armament , the ships were considered to be semi - dreadnoughts , a transitional stage between pre - dreadnought s with their light intermediate armament and dreadnoughts solely equipped with large guns . Description . The construction of was delayed since she could not be laid down until the slipway occupied by the armored cruiser 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 " . The crew ranged from 800 to 940 officers and enlisted men . " Satsuma " had an overall length of , a beam of , and a normal draft of . She displaced at normal load . " Aki " was long overall , had a beam of , and the same draft as her half - sister . She displaced at normal load . Propulsion . " Satsuma " was powered by a pair of vertical triple - expansion steam engines , each driving one propeller shaft , using steam generated by 20 Miyabara water - tube boilers using a mixture of coal and fuel oil . The engines were rated at a total of and designed to reach a top speed of . During the ship ' s sea trials she reached from . " Satsuma " carried a maximum of of coal and of oil which allowed her to steam for at a speed of . Unlike her half - sister , she only had two funnels . " Aki " was intended use the same type of engines as her sister , but the IJN decided fit her with a pair of Curtiss steam turbine sets after she was launched in 1907 . The turbines each powered one propeller shaft using steam from 15 Miyabara boilers . The turbines were rated at a total of for a design speed of . The ship reached a top speed of during her sea trials from . She carried a maximum of of coal and of oil gave her the same range as her half sister . Armament . The ships were completed with four 45 - caliber 12 - inch 41st Year Type guns in two gun turrets , one each fore and aft of the superstructure . They fired armor - piercing ( AP ) shells at a muzzle velocity of ; this gave a maximum range of . The intermediate armament was much more numerous than in the preceding " Katori " class , with six twin - gun turrets equipped with 45 - caliber Type 41 10 - inch guns , three turrets on each side of the superstructure . The guns had a muzzle velocity of when firing shells . The other major difference between the two ships was that " Aki " s secondary armament consisted of eight 45 - caliber 6 - inch 41st Year Type guns , mounted in casemate s in the sides of the hull . The gun fired a AP shell at a muzzle velocity of . " Satsuma " , in contrast , was equipped with a dozen 40 - caliber 4 . 7 - inch 41st Year Type quick - firing ( QF ) guns , mounted in casemates in the sides of the hull . The gun fired a shell at a muzzle velocity of . The ships were also equipped with four ( " Satsuma " ) or eight ( " Aki " ) 40 - caliber 12 - pounder 12 - cwt QF guns and four 28 - caliber 12 - pounder QF guns . Both of these guns fired shells with muzzle velocities of and respectively . In addition , the battleships were fitted with five submerged torpedo tube s , two on each broadside and one in the stern . Armor . The waterline main belt of the " Satsuma " - class vessels consisted of Krupp cemented armor that had a maximum thickness of amidships and tapered to a thickness of inches at the ends of the ship . A strake of armor protected the casemates . The barbettes for the main guns were thick . The armor of " Satsuma " s main gun turrets had a maximum thickness of inches and those of " Aki " were an inch thicker . The deck armor was thick and the conning tower was protected by six inches of armor . Service . 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 battlecruiser s in 1910 and did not include them . " Aki " was refitting at Kure and " Satsuma " was assigned to the 1st Battleship Squadron when World War I began in August 1914 . 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 . " 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 . 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 . 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 . 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 and the battleship in Tokyo Bay on 2 September 1924 ; " Satsuma " was sunk by the battleships and five days later in the same area .