Katō Hiroharu was born in
Fukui City in
Fukui on 2 November in the 3rd year of
Meiji (23 December 1870) as the eldest son of one of the first navy officers, Katō Naokata, of
Fukui Domain in Imperial Japan before the
abolition of the han system. On 17 July 1891, he graduated top of the class from
Imperial Japanese Naval Academy, 18th class. He was assigned to cruiser as a cadet as of 20 May 1892 and experienced two tours to
Kingdom of Hawaii. While at
Honolulu on the second tour, he was promoted to ensign on 1 March 1894. He was assigned as a navigator on cruiser . After returning to
Yokosuka Naval Base, he completed the Gunnery training program on corvette on 1 March 1896, which later became the Gunnery School of
Naval War College. At the same time, he was assigned as a navigator on cruiser . In February 1896, he married Murata Chiyoko from the
Fukui Domain, and on 24 October 1896, he was appointed as a member of the receiving commission sent to London for battleship . Kato fought against the treaty limitations, and the treaty of 1936, finally dying after writing his memoirs, widely regarded as a treatise on why Japan was disadvantaged by the treaties. His actions prevented him from advancing in rank and probably cost him a seat in the government. He had an active antagonistic relationship with
Yamamoto, who used his influence to prevent Kato from advancing. ==Imperial Japanese Court Ranks==