No.1-class submarine chaser

The No. 1-class submarine chaser (第一号型駆潜艇) was a class of submarine chasers of the Imperial Japanese Navy (IJN), serving during World War II. Three vessels were built in 1933-36 under the Maru 1 Programme and the Maru 2 Programme. They have two sub classes.

Background

 * In World War I, German U-boat raged. The IJN began maintenance of an anti-submarine boat as a lesson in this, because Japanese shoreline and sea-lanes were very long. The IJN had some submarine chaser type tugboats and yard ferries. However, they were small and their speed was low.
 * The IJN wanted to give the anti-submarine boats a speed of more than 20 knots, because their Kaidai III submarine already achieved a 20kt surfaced.

Design

 * The Naval Technical Department (Kampon) made draft shallow to give them high speed. They achieved 24 kt speed hereby.
 * The No. 1 and the No. 2 were completed in March 1934, and they were assigned to the 1st Submarine Chaser Division, Yokosuka Naval Defence Squadron.
 * However, because of their very shallow draft they lacked the rolling performance. This fact become evident after the Tomozuru incident.
 * The Tomozuru incident affected the No. 1-class. The No. 1 and the No. 2 were sent to the Uraga Dock Company in July 1934, and repairs were started. They were equipped 80 tons ballast and mounted a ballast keel. The drawings for the No. 3-class boat was also revised.

Service

 * Late 1934, Repairs were completed.
 * October 1936, The No. 3 assigned to 1st SchDiv. They always shared an action afterward.
 * In 1938, the 1st SchDiv was transferred to the No. 1 Base Force (Shanghai).
 * On 5 September 1941, the No. 1 Base Force was transferred to the 2nd Fleet.
 * In December 1941 – March 1942, the 1st SchDiv engaged to the Battle of the Philippines and Dutch East Indies campaign.
 * On 10 March 1942, the 1st SchDiv was transferred to the No. 21 Special Base Force (Surabaya), 2nd Southern Expeditionary Fleet, Southwest Area Fleet.
 * On 1 May 1942: The 1st SchDiv was dissolved. They spent all their time for escort operations in the Java Area.

No.1-class

 * Project number was K3. 2 vessels were built under the Maru 1 Programme. They equipped the MV hydrophone by Submarine signal company and latest active sonar the Type 93.

No.3-class

 * Project number was K4. Only 1 vessel was built under the Maru 2 Programme. The No. 3 was equipped the French SCAM active sonar and latest hydrophone the Type 93. The No. 3 was classed in the No. 1-class in the IJN official documents.