Sent to England for study in 1877, Ijūin completed courses at Royal Naval College, Greenwich and was commissioned a sub-lieutenant on 27 November 1883. Promoted to lieutenant on 20 June 1885, he returned to work on the Imperial Japanese Navy General Staff (1886–99). He was promoted to lieutenant-commander on 16 October 1890 and received a double promotion to captain on 7 December 1894. During the First Sino-Japanese War he served as a staff officer at the Imperial Japanese Navy headquarters. He became a close confidant of navy chief Admiral Yamamoto Gonnohyoe, and was an important planner and specialist in naval technology.
Promoted to rear admiral on 26 September 1899, Ijūin was a strong proponent of better relations between Japan and the United Kingdom, and worked to develop the Anglo-Japanese Alliance (1902) from behind the scenes. He was on a diplomatic mission to the United Kingdom in 1902 with Major-General Fukushima Yasumasa, and was awarded an honorary Knight Commander of the Order of the Bath (KCB).[2] He was promoted to vice-admiral on 5 September 1903. As an engineer, he also developed the "Ijūin Fuse," making use of the newly developed Shimose powder, which was successfully used in heavy naval artillery shells during Russo-Japanese War (1904–05).
While commander in chief of the Combined Fleet, Ijūin developed a reputation for being fanatical about training, leading to a popular song among sailors that a week in the Japanese navy was "Monday-Monday, Tuesday, Wednesday, Thursday, Friday-Friday" (月月火水木金金, 'Getsu Getsu Ka Sui Moku Kin Kin).
Ijūin was elevated to the title of danshaku (baron) in 1907 under the kazoku peerage system, became an admiral on 1 December 1910 and marshal-admiral on 26 May 1917, despite never having actually commanded a ship.
His grave is at Aoyama Cemetery in Tokyo. His son, the Admiral Ijūin Matsuji, also a career navy officer, perished in World War II during the Battle of Saipan in 1944. His second son Takeji Ohno was 4th captain of the battleship Yamato.
Hoare, J.E. (1999). Britain and Japan: Biographical Portraits, Vol. III. California, USA: RoutledgeCurzon. ISBN1-873410-89-1.
Schencking, J. Charles (2005). Making Waves: Politics, Propaganda, And The Emergence Of The Imperial Japanese Navy, 1868-1922. California, USA: Stanford University Press. ISBN0-8047-4977-9.
