Acting envoy to the United States Ono Tomogoro discovered "Stonewall" in the Washington Navy Yard in May and made a formal offer to the United States government for the purchase of the ironclad. The purchase was concluded for the price of $400,000 and she was turned over to the Japanese on 5 August who renamed her "Kōtetsu". However, by the time of her arrival in Shinagawa harbor on 22 January 1868, the Boshin War between the shogunate and pro-Imperial forces had begun, and the United States took a neutral stance, stopping the delivery of military material, including the delivery of "Kōtetsu", to the Shogunate. The ship had arrived under a Japanese flag with an American crew, but US Resident-Minister Robert B. Van Valkenburg ordered her put back under the American flag. "Kōtetsu" was finally delivered to the new Meiji government in early March 1869.