Tsuboi Kōzō was born as Hara Kōzō, the second son of a doctor in what is now part of Hōfu, Yamaguchi, and was adopted into the Tsuboi family as a child. As a Chōshū Domainsamurai he took part in the defense of the city during the bombardment of Shimonoseki by European warships from September 5 to 8, 1864. Witnessing firsthand the firepower and devastation caused by a relatively few Western warships, Tsuboi became convinced Japan must also obtain this weaponry to survive. He enlisted in the Chōshū domain navy later that year and served aboard the Kigai-maru, while studying English and navigation at the Chōshū Naval School.
Returning to Japan in 1874, Tsuboi was promoted to lieutenant commander. His first command was as captain of the Dai Ichi Teibō from August 3, 1874. From 1875 through 1879, he surprised warship construction at the Yokosuka Naval Arsenal; however, he was injured in an accident in August 1878 which required two months hospitalization. On his return to active status in February 1879, he served as commander of various ships, including the paddle corvette Jingei, gunboat Banjō, corvette Nisshin and corvette Kaimon, and various shore posts until 1889 (including Deputy Director of the Imperial Japanese Navy Technical Department. He returned to sea as captain the cruiser Takachiho from April 1889 to September 1890, serving simultaneously as chief-of-staff of the Readiness Fleet.
In command of the Readiness Fleet during the First Sino-Japanese War, Tsuboi was at the Battle of Pungdo in command of the Yoshino, and later won distinction at the Battle of the Yalu on September 17, 1894, where (as commander of the Flying Squadron), he displayed innovative tactics and aggressive maneuvers against the Chinese Beiyang Fleet.
A national hero following the war, Tsuboi was ennobled with the title of danshaku (baron) under the kazoku peerage system on August 20, 1895, and promoted to vice admiral the following year. In 1896 he was made Commander in Chief of the Readiness Fleet, and in 1897, Commander of the Yokosuka Naval District. He died of cancer in 1898. His grave is at the temple of Zuisho-ji, in Shirogane-dai, Tokyo.
Schencking, J. Charles (2005). Making Waves: Politics, Propaganda, And The Emergence Of The Imperial Japanese Navy, 1868–1922. Stanford University Press. ISBN0-8047-4977-9.
Volpicelli, Zenone. The China-Japan War, London, 1896.
