Board Thread:Event Community Discussion/@comment-28069733-20170521154728/@comment-1637496-20170527175752

Ar-cen-ciel wrote: This page? Should we make a "trivia" heading? Is this too long?
 * Historian editors are free to provide notes in the ship class descriptions.

Developed originally as fishery protection ships, with a secondary minesweeping and convoy escort wartime function, the Shimushu class coastal defence ships became the template for the main oceanic convoy escorts built by the IJN during the war. These ships were initially conceived in the early 1930s, a resurgent Russian naval presence in the Far East resulted in a number of incidents involving Japanese fisheries in disputed waters, they were consistent with the unlimited category of the London Naval Treaty of 1930 that allowed to build ships like the British sloops, French avisos and the two ships Erie class patrol gunboats, but they were effectively built only after Japan left the Treaty system and the Second London Naval Treaty had removed those quantitative limitations that justified the introduction of an unlimited category. Originally coastal defence ship referred to obsolete battleships and cruisers relegated to coastal defence, it became a separate typology that included only the new escorts in July 1942, the surviving obsolete armoured cruisers were reclassified as heavy cruisers; the new classification was also moved from the gunkan sub-group, which included main combatants like battleships, cruisers, carriers, etc. to the baseline kantei group, which included destroyers.

Coastal defence ships are divided into six classes: Shimushu, Etorofu, Mikura, Ukuru, No.1 and No.2. Some authors rate the Hiburi class, which were hybrids between the Mikura and Ukuru built only by Hitachi, as a separate class, but others consider them to be part of the Ukuru class. The official classification consisted of:

Type A: Shimushu, Etorofu, Mikura, Ukuru

Type C: No.1

Type D. No.2

but as designed they had been originally divided into:

Type A: Shimushu, Etorofu

Tybe B: Mikura

Modified Type B: Ukuru

Type C: No.1

Type D: No.2

The lack of an ASW emphasis in the Shimushu class can be evinced from the limited depth charge stowage (12, increased to 24 since May 1942 and 60 since Autumn 1943) and the lack of sonar until Autumn 1942, coastal defence ships became genuine, purpose-built, convoy escorts only with the Mikura class, that was fitted with sonar since the beginning and carried 120 depth charges. Mass production wasn't attempted until the Ukuru class and the Type C&D, which extensively employed welding and pre-fabrication.

During WWII the kaibokan classification was also used for the two former Chinese light cruisers Ning Hai and Ping Hai, in late 1943 the IJN decided to rebuild the two idle ships into escorts with a radically altered superstructure and a lighter armament analogous to the Type C&D kaibokan, they were respectively renamed Iaoshima and Isoshima. These relatively large ships were also supposed to serve as tenders for aircraft bases, for this purpose they were equipped with a crane on the mainmast, trucks and one daihatsu (14-m) and one shohatsu (10-m) landing crafts. On 25 September 1944 Yasoshima was re-rated as light cruiser because of administrative reasons, it had been decided to appoint her as flagship for the newly organised First Transport Squadron.