Classe Ukuru

The Ukuru-class escort ships were a class of twenty kaibōkan escort vessels built for the Imperial Japanese Navy during World War II. The class was also referred to by internal Japanese documents as the "Modified B-class" coastal defense vessel, and they were the fourth class of kaibōkan. The escort ship was developed after the start of the Pacific War, it became apparent that a design more capable of anti-submarine warfare than the previous and kaibōkan was needed. Despite being a simplified design, the Mikura-class vessels still took too long to construct, and due to the high attrition of Japan's destroyer and escort ships, action needed to be urgently taken to produce more ships in a quicker time. Furthermore, operational experience had shown that the Mikura-class was still very weak in its anti-aircraft capability. The first five of the new Ukuru-class were authorized under the 1941 Rapid Naval Armaments Supplement Programme and an additional six in the 1942 Modified 5th Naval Armaments Supplement Programme and nine under the 1944 Wartime Naval Armaments Supplement Programme. Twenty vessels were commissioned; two more (Urumi and Murotsu) were launched by Uraga Dock and completed in August 1945 but were still uncommissioned by the war’s end. In addition to these, nine units and two additional unfinished ships belong to a sub-class called the Hiburi class and are included in the table below. The Ukuru-class was a further simplification of the Mikura design. The hull was constructed using prefabricated sections which avoided the use of shaped steel or curved plates, which greatly reduced construction time. The curved plates on the bridge were also eliminated, and the smoke stacks were made of hexagonal elements instead of with a circular or oval cross-section. Internally, individual crew quarters were eliminated, becoming a communal area, and overall the construction was very spartan. These changes reduced construction time to under four months, although construction was often hindered by the lack of diesel engines.