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	(left to right) No. 1, No. 2 and No. 3 in 1938
Class overview
Name	No. 1-class submarine chasers; No. 1 class (Project number K3); No. 3 class (Project number K4);
Builders	Uraga Dock Company; Tōkyō Ishikawajima Shipyard; Asano Shipyard;
Operators	Imperial Japanese Navy
Succeeded by	No. 4 class
Cost	1,525,700 JPY (No. 1-class); 1,530,000 JPY (No. 3-class);
Built	1933 – 1936
In commission	1934 – 1946
Planned	3
Completed	3
Lost	1
Retired	2
General characteristics No. 1-class
Displacement	266 long tons (270 t) standard; 280 long tons (284 t) trial; and after late 1934; 377 long tons (383 t) trial;
Length	65.30 m (214 ft 3 in) overall; 64.00 m (210 ft 0 in) waterline;
Beam	5.90 m (19 ft 4 in)
Draught	1.43 m (4 ft 8 in)
Propulsion	2 × Kampon Mk.22 Model 8 diesels; 2 shafts, 3,400 bhp;
Speed	24.0 knots (27.6 mph; 44.4 km/h); and after late 1934; 21.1 knots (24.3 mph; 39.1 km/h);
Range	1,500 nmi (2,800 km) at 14 kn (16 mph; 26 km/h)
Complement	65
Armament	2 × 40 mm heavy machine guns; 36 × depth charges; 1 × depth charge thrower; 1 × Type 93 active sonar; 1 × MV hydrophone;
General characteristics No. 3-class
Displacement	270 long tons (274 t) standard; 285 long tons (290 t) trial;
Length	56.10 m (184 ft 1 in) overall; 55.00 m (180 ft 5 in) waterline;
Beam	5.60 m (18 ft 4 in)
Draught	2.10 m (6 ft 11 in)
Propulsion	2 × Kampon Mk.22 Model 6 diesels; 2 shafts, 2,500 bhp;
Speed	20.0 knots (23.0 mph; 37.0 km/h)
Range	1,500 nmi (2,800 km) at 14 kn (16 mph; 26 km/h)
Complement	60
Armament	2 × 40 mm heavy machine guns; 36 × depth charges; 2 × Type 94 depth charge projectors; 1 × depth charge thrower; 1 × French SCAM active sonar; 1 × Type 93 hydrophone;

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^[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.

Bibliography

Ships of the World special issue Vol. 45, Escort Vessels of the Imperial Japanese Navy, "Kaijinsha"., (Japan), 1996.
The Maru Special, Japanese Naval Vessels No. 49, Japanese submarine chasers and patrol boats, "Ushio Shobō". (Japan), 1981.