# No.1-class submarine chaser

The No. 1-class submarine chaser (第一号型駆潜艇, Dai 1 Gō-gata Kusentei) 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.

## Ships in classes
### 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.
| Ship | Builder | Laid down | Launched | Completed | Fate |
| No. 1 | Uraga Dock Company | 19 June 1933 | 23 December 1933 | 24 March 1934 | Scuttled by Royal Navy off Singapore on 11 July 1946. Decommissioned on 10 August 1946. |
| No. 2 | Tōkyō Ishikawajima Shipyard | 9 June 1933 | 20 December 1933 | 25 March 1934 | Sunk by USS Blueback at north of Lombok on 27 June 1945. |

### 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.
| Ship | Builder | Laid down | Launched | Completed | Fate |
| No. 3 | Asano Shipyard | 17 April 1935 | 6 June 1936 | 5 October 1936 | Scuttled by Royal Navy off Singapore on 11 July 1946. Decommissioned on 10 August 1946. |

## Photos

* No. 2 in 1934
* No. 3 in 1936

## Footnotes

* ↑ Submarine chaser No. 1 (第1号駆潜艇, Dai 1 Gō Kusentei). The same shall apply hereinafter.