Japanese ironclad Kōtetsu , later renamed was the first ironclad warship of the Imperial Japanese Navy . Built in France in 1864 for the Confederate States Navy as CSS " Stonewall " , and acquired from the United States in February 1869 , she was an ironclad ram warship . She had a decisive role in the Naval Battle of Hakodate Bay in May 1869 , which marked the end of the Boshin War , and the complete establishment of the Meiji Restoration . Her sister ship " Cheops " was sold to the Prussian Navy , becoming the " Prinz Adalbert " . Origins . " Kōtetsu " was built by shipbuilder L ' Arman in Bordeaux , France . Originally named " Sphynx " , this ship was initially built for the Confederate Navy during the American Civil War . In June 1863 John Slidell , the Confederate commissioner to France , asked Emperor Napoleon III in a private audience if it would be possible for the Confederate government to build ironclad warships in France . Arming ships of war for a recognized belligerent like the Confederate States would have been illegal under French law , but Slidell and Confederate agent James D . Bulloch were confident that the French emperor would be able to circumvent his own laws more easily than could the British government . Napoleon III agreed to the building of ironclads in France on the condition that their destination remain a secret . The following month Bulloch entered a contract with Lucien Arman , an important French shipbuilder and a personal confidant of Napoleon III , to build a pair of ironclad rams capable of breaking the Union blockade . To avoid suspicion , the ships ' guns were manufactured separately in England and they were named " Cheops " and " Sphynx " to encourage rumors that they were intended for the Egyptian navy . Prior to delivery , however , a shipyard clerk walked into the U . S . Minister ' s office in Paris and produced documents which revealed that L ' Arman had fraudulently obtained authorization to arm the ships and was in contact with Confederate agents . The French government blocked the sale under pressure from the United States , but L ' Arman was able to sell the ships illegally to Denmark and Prussia , which were then fighting on opposite sides of the Second Schleswig War . " Cheops " was sold to Prussia as " Prinz Adalbert " , while " Sphynx " was sold to Denmark under the name " Stærkodder . " Manned by a Danish crew , the ship left Bordeaux for its shakedown cruise on June 21 , 1864 . The crew tested the vessel while final negotiations were being conducted between the Danish Naval Ministry and L ' Arman . Intense haggling over the final price and a disagreement over compensation from L ' Arman for late delivery led to his calling off the deal on October 30 . The Danish government refused to relinquish the vessel , claiming confusion in regards to the negotiations . American career as CSS " Stonewall " . On January 6 , 1865 the vessel took on a Confederate crew at Copenhagen under the command of Captain T . J . Page , CSN and was recommissioned the CSS " Stonewall " while still at sea . The arrival of the " formidable " " Stonewall " in America was dreaded by the Union , and several ships tried to intercept her , among them the USS " Kearsarge " and the USS " Sacramento " . " Stonewall " sprang a leak , however , after leaving Quiberon , Brittany and Captain Page steamed her into Spain for repairs . In February and March , USS " Niagara " and " Sacramento " kept watch from a distance as " Stonewall " lay anchored off Corunna during February 1865 . On March 24 Captain Page steamed the " Stonewall " out to sea , challenging the U . S . Navy vessels , which turned and fled , fearful of engaging the ironclad . Finding that the enemy had run , Captain Page steamed for Lisbon , intending to cross the Atlantic Ocean from there and attack at Port Royal , the base of Major General Sherman ' s attack on South Carolina . " Stonewall " reached Nassau on May 6 , and then sailed on to Havana , Cuba , where Captain Page learned of the war ' s end . There he decided to turn her over to the Spanish Captain General of Cuba for the sum of $ 16 , 000 . The vessel was then turned over to United States authorities in return for reimbursement of the same amount . She was temporarily de - commissioned , stationed at a U . S . Navy dock , until she was offered for sale to the Japanese government of the Tokugawa shogunate . Japanese career . " Kōtetsu " was supposed to be delivered to the Tokugawa shogunate in 1868 , in order to reinforce the ongoing modernization of its army and navy . US $ 30 , 000 had already been paid , and the remaining US $ 10 , 000 were to be paid on delivery . When the Boshin War between the shogunate and pro - Imperial forces broke out however , Western powers took a neutral stance , retrieved any military advisors they had in Japan , and stopped the delivery of military material , including the delivery of " Kōtetsu " to the shogunate . The ship actually arrived under Japanese flag , but US Resident - Minister Van Valkenburgh ordered her put back under American flag on arrival in Japan under a caretaker crew of the US naval squadron then stationed there . " Kōtetsu " was finally delivered to the new Meiji government in February 1869 . She was immediately put to use and dispatched with seven other steam warships to the northern island of Hokkaidō , to fight the remnant of the Shogun ' s forces , who were trying to form an independent Ezo Republic there , with the help of French ex - military advisors . On March 25 , 1869 , in the Naval Battle of Miyako Bay , " Kōtetsu " successfully repulsed a surprise night attempt at boarding by the rebel " Kaiten " ( spearheaded by survivors from the Shinsengumi ) , essentially thanks to the presence of a Gatling gun on board . She then participated in the invasion of Hokkaidō and various naval engagements in the Naval Battle of Hakodate Bay . " Kōtetsu " was renamed " Azuma " in 1871 and remained in military service until 1888 , when she was turned to non - combat harbor service . " Kōtetsu " was well - armed with casemate d rotating turret guns , and considered a " formidable " and " unsinkable " ship in her time . She could sustain direct hits without her armour being pierced , and prevail against any wooden warship . In effect , Japan was thus equipped with advanced ironclad warships only ten years after the launch of the first ocean - going ironclad warship in history , the French Navy ' s " Gloire " ( " Glory " , launched in 1859 ) .