Japanese battleship Ise
On 12 April 1922, while at Yokohama, "Ise" hosted a delegation which included the Prince of Wales (the future King Edward VIII), who was accompanied by his second cousin, the future Lord Mountbatten of Burma. Captain Kanna Norikazu relieved Nagasawa on 1 December. The ship aided survivors of the Great Kantō earthquake in September 1923. From the early 1920s through the late 1930s, "Ise" mostly cruised off the coast of China. Little detailed information is available about her activities during the 1920s, although she helped sink the obsolete destroyer during gunnery training on 10 August 1926. The ship was overhauled in 1928–1929, during which her forward superstructure was enlarged and her aviation facilities improved.
Italian submarine Iride
"Iride" secretly participated in the Spanish Civil War, being a part of two incidents that strained Italo-British relations. She carried out a mission from 24 August – 5 September 1937 under command of Junio Valerio Borghese. On August 26, "Iride" arrived at her designated area between Ibiza and Cape San Antonio. During the patrol she attempted attacks 8 times, but only fired on two of those. In the evening of August 29, she sighted a cargo ship heading towards Valencia, and attacked it twice, second time from 600 meters, and both were unsuccessful. At 20:45 on August 30, 1937, while traveling on the surface, she sighted British destroyer steaming from Valencia to Gibraltar, and mistaking it for a Spanish naval ship of the , launched a 450mm torpedo from 700 meters at 20:52. managed to avoid the torpedo with a sharp turn to the starboard, and then went on to search for the submarine using her sonar. However, the sonar showed a different position than where the submarine was sighted, and proceeded to launch depth charges on the sonar location. British destroyers , and , and a cruiser joined in, and continued the attack for nine hours. "Iride" hiding at a great depth managed to survive and did not sustain any serious damage.