CSS Stonewall, a 1390-ton ironclad ram, was built in Bordeaux, France, for the Confederate Navy. Embargoed by the French government in February 1864, prior to her launching, she was subsequently sold to Denmark under the name Stærkodder. Upon completion of her construction in late 1864, the Danish government would not accept delivery and her builder secretly resold her to the Confederates.

Commissioned at sea as CSS Stonewall in October 1864, the ironclad ram put to sea on March 24, 1865. Stonewall was well-armed with casemated rotating turret guns, and well-armoured. The Stonewall was considered a "formidable" and "unsinkable" ship in her time. The arrival of the Stonewall in North America was dreaded by the United States, and several ships tried to intercept her, among them the USS Kearsarge and the USS Sacramento. After calling at Lisbon, Portugal, the Confederate ironclad crossed the Atlantic, reaching Havana, Cuba, in May. As the Civil War had then ended, she was turned over to Spanish Authorities.

In July 1865, the Spanish delivered Stonewall to the United States Government. She was laid up at the Washington Navy Yard, D.C., for the next two years, and then sold to Japan.

In Japanese service, she was initially named Kôtetsu (Japanese: literally "Ironclad"), and was the first ironclad warship of the Imperial Japanese Navy. She had a decisive role in the Naval Battle of Hakodate in May 1869, which marked the end of the Boshin War, and the complete establishment of the Meiji Restoration. It was said that she could sustain direct hits without her armour being pierced, and prevail against any wooden warship. Kôtetsu was renamed Azuma (Japanese: "East") after 1871, and was broken up for scrap January 28, 1888.