was the lead ship in the two-ship of light cruisers of the Imperial Japanese Navy. Tenryū was named after the Tenryū River in Nagano and Shizuoka prefectures.
Background
The Tenryū-class was designed to act as flagships for destroyer flotillas. The design represented an intermediate class between the light cruiser and the destroyer, which had few counterparts in other navies of the time, although it was inspired by a similar concept to the Royal Navy's and s. The Imperial Japanese Navy and Japanese shipbuilding industry were still closely associated with the British due to the Anglo-Japanese Alliance, and were able to improve on the British experience.
Design
The Tenryū-class vessels, termed "small-model" (or "3,500-Ton") cruisers, were designed as fast flotilla leaders for the Imperial Navy's new first- and second-class destroyers. With improvements in oil-fired turbine engine technology and the use of Brown Curtiss geared turbine engines, the Tenryū class had more than twice the horsepower of the previous , and were capable of the high speed of , which was deemed necessary in their role as flagships for destroyer squadrons. However, by the time of their completion, newer Japanese destroyers, such as the had a design speed of 39 knots, and newer American cruisers, such as the also exceeded it in firepower.
However, in terms of weaponry, the Tenryū class was weaker than any other contemporary cruiser. The main battery consisted of four 14 cm/50 3rd Year Type naval guns, which were also utilized as the secondary battery on the s. However, the guns were situated in single mounts on the centerline, with only a limited angle of fire, and could fire only one gun at a target immediately in front or aft of the vessel. A further weakness was the lack of room for anti-aircraft guns. Despite awareness increasing about the growing threat of aircraft to surface ships, the secondary battery of the Tenryū class consisted of only a single dual-purpose 8 cm/40 3rd Year Type naval guns, plus two 6.5 mm machine guns. The class also was the first to use triple torpedo launchers, with two centerline-mounted Type 6 21-inch launchers. No reloads were carried.
Service history
Early career
Tenryū was completed on 20 November 1919, at the Yokosuka Naval Arsenal, and was assigned as flagship of the 2nd Destroyer Squadron based at Kure Naval District, under the IJN 2nd Fleet.
The following year, Tenryū was assigned to patrols of the east coast of Russia, providing support to Japanese troops in the Siberian Intervention against the Bolshevik Red Army. She was transferred to the reserves at Kure on 20 April, but was reactivated from 1 December 1921 - 1 December 1922, and again from 1 December 1923 – 1 December 1925, alternating active duty periods with her sister ship Tatsuta as flagship of the 1st Destroyer Squadron. From 5 February 1927, she was assigned to patrols of the mouth of the Yangtze River.
After minor renovation in late 1927, Tenryū once again became flagship of the 1st Destroyer Squadron. From 1 December 1928, she was assigned back to Kure, serving as a training vessel for the Imperial Japanese Navy Academy and Submarine School. In 1930, she was given a tripod foremast.
On 9 October 1931, Tenryū was assigned to patrols of the Yangtze River in China as part of the IJN 3rd Fleet, and was thus in combat during the January 28 Incident at Shanghai in 1932. She returned to Japan in October 1933, and from November 1934 was again based at Kure. On 26 September 1935, during fleet maneuvers in a typhoon, Tatsuta (along with several other vessels) suffered hull damage in what later came to be known as the Fourth Fleet Incident. Repair work at Kure Naval Arsenal lasted until May 1936.
From November 1936, Tenryū was paired with her sister ship Tatsuta in the 10th Cruiser Squadron of the IJN 3rd Fleet, replacing the cruiser . As the situation between Japan and China deteriorated into the Second Sino-Japanese War, Tenryū supported the landings of the Imperial Japanese Army and Japanese naval forces in Shanghai, and the blockade of the Chinese coast. As a component of the IJN 5th Fleet, on 10 May 1938 she covered the landing of Japanese forces at Amoy and on 1 July 1938 supported operations in Guangzhou. Tatsuta and Tenryū operated in Chinese waters until 14 December 1938, when they were withdrawn from front line service and assigned to the reserves. From 1 December 1939, Tenryū was based at Maizuru Naval District as a guard ship and training vessel for the Imperial Japanese Navy Engineering Academy.