Ukuru class escort (1944) – Naval Encyclopedia

Japan, 32 Improved Type B Escort (kaibōkan), built 1944-45 (some incomplete).

The Ukuru or “improved type B” were an attempt to simplify the design of the Mikura class escorts, developed after the start of the Pacific War and far better for anti-submarine warfare than the Shimushu and Etorofu class kaibōkan. They took still too long to manufacture in a context of massive attrition. So not only the Ukuru design cut many corners, but it also integrated recent operational experience to integrate more anti-aircraft capability. The first five Ukuru-class were authorized under the 1941 Rapid Naval Armaments Supplement Programme, then six in the 1942 Modified 5th Naval Armaments Supplement Programme, nine under the 1944 Wartime Naval Armaments Supplement Programme. Twenty in all commissioned, with two more (Urumi and Murotsu) still uncommissioned on V-Day plus nine of the sub-class Hiburi were never completed.

IJN Shionan (colorized by Irootoko Jr)

Development

The Mikura, Chidori and Etorofu were consequences of the 1930 London Naval Treaty, limiting total IJN destroyer tonnage, leading to use a loophole for ships between 600 and 2,000 tons with no more than four guns over 76mm, no torpedoes, maximum speed 20 knots. Under 600 tonnes all was free. Naturally the IJN staff back in 1930 was eager to exploit the latter category and stacked as much “stuff” they could on torpedo boats. However the Tomozuru affair recalled this was wishful thinking and the Japanese TB lineage was cut short. However, before the war, Japan also needed guardships, and started to look at “improved guard ships” that could work for dedicated patrol and ASW. After the Shimushu class, a very expensive an neat exercises by Mitsubishi (in-house) for the Navy, the latter found it impractical for a marge production leading to the design of the Etorofu class, still released under the obsolete designation of kaibōkan (Kai = sea, ocean, Bo = defence, Kan = ship) used for obsolete battleships reassigned to coastal defense duties.

IJN Shionan in 1944

When the Pacific War started, the IJN started to think of freeing more fleet destroyers from escort duties, and thus looked at building even more anti-submarine warfare focused escort, with longer range and better seaworthiness than its traditional sub-hunters. Parallel to the Etorofu appeared through the 1941 Rapid Naval Armaments Supplement Programme the “Type B” escorts, Mikura-class. They were in essence, a simplified version of the Etorofu-class with a better focus on ASW capabilities. They came however in limited production to “test the waters” of this new design, for a possible future mass production. And indeed, it was soon apparent that they were still too costly and complicated to built. But in late 1942, US carrier air groups were taken far more seriously and by 1943 it was obvious that the next escorts woiuld need also a better anti-aircraft capability, alongside the ASW existing assets.

This led to the design of the Ikuru class, a Type B escort that would be geared towards even more simplifications towards mass production at last. To achieve this, the hull was constructed using prefabricated sections instead of shaped steel or curved plates, all made on purpose previously. But that implied the use of master molding elements. Engineers chased off all and any curved plating, with the bridge now squat, the prow having almost no flare with curved plates, instead just lower and higher plates were joined in some sort of knuckle forward. Also the lower hull use forward V shape cross-sections. The only “complex” part remained the bow tip. Hull lines were preserved through, but any complicated shape was eliminated. The stern was a flat transom. The smoke stacks were made of hexagonal elements (no longer oval cross-section) and internally, individual crew quarters were eliminated and made into communal areas. Anything that could take time was removed, making for a very spartan, not popular vessel class in service to say the least.

However this all reduced construction time to under four months, with the only bottleneck and delays resulting from the absence of diesel engines, which were still made “the old way”. With them being simplified as much, although this was far less easy, construction time could have fell dramatically to just two months, still far from the Kaiser’s yards prowesses back in the US, but brilliant and unprecedented for a Japanese design. And this came at last with a better shipyard organization to also speed time to gather, store, redistribute materials and start prefabrications of complex elements in advance of final assembly. German modular manufacturing techniques by 1944 were probably part of the package sent to Japan by submarines.

Design of the class

The Ikuru was a simplified Mikura, which itelf was a simplified Etorofu class. Unlike the previous Shimushu, the “Type A-modified” kept a high freeboard, inheritance from Kuriles waters patrol, new hull simplified hull shapes, a more universal and simpler bow, long forecastle with almost no flare, and excellent stability given the “fuller lines” making for extra buoyancy. The Mikura already had with bulkheads without manholes, stern and bridge structure reworked and simplified, so the Ukuru built on these fundations and was stripped bare to the very essentials. The crew was now of 150 officers and ratings, a bit more than prior ships due to the extra AA planned from the very start.

Hull and general design

The Ukuru class had still a stepped bridge, faceted smokestack, still an aft deckhouse, and same main guns as the Mikura but the reserve of stability and buoyancy were used to the full to fi as many AA as possible without compromising the metacentric height. In size, they were very identical down to the same number of members and general shapes of the Etorofu, at still the same 77.79 meters (254 ft 12 in) overall, 72.5 meters between parallels, 77.5 meters at the waterline, and 78.8 meters overall to be exact. For a beam of 9.1 meters (29 ft 10 in) and a draft of 3.05 meters (10 ft). They displaced even less, at 940 versus 960 metric tons (930 long tons) under standard load and deeply load some 1,020 tonnes. All these simplifications also saved a lot of metal and weight.

Powerplant

The Ukuru class like the Mikura and Type B escorts had the same two geared diesel engines, each driving its own propeller shaft, for a full rating of 4,400 brake horsepower (3,300 kW) and top speed of 19.5 knots (36.1 km/h; 22.4 mph). Range was still the same 5,000 nautical miles (9,300 km; 5,800 mi) at 16 knots (30 km/h; 18 mph), extended even further at 10 knots.

Armament

The Ukuru class were as much AA escorts than ASW ones. The main battery was the same as on the Mikura-class: They had three dual-purpose Type 10 120 mm AA guns: One forward single and a twin mount aft for stability, but the later ships were fitted with modified gun shields.
The anti-aircraft capability now included no less than five triple-mount Type 96 25 mm (1 inches) Type 96 anti-aircraft guns: Two abreast the bridge, one abaft the smokestack, one aft on the deck house, and a single-mount forard of the bridge in a top mount.
Some also received extra single-mount Type 96s, located on the forecastle. They all also received from the start, the latest Type 22 and Type 13 radar. Initially the depht charge provision was of 120 depth charges, with two Type 94 depth charge projectors as well as sixteen Type 3 depth charge throwers, two depth charge chutes, at the stern. To go with these, they had the model 93 sonar and Type 93 hydrophone (see below). Later the former was replaced by the Type 3 Model 2 sonar. Others also receive a 8 cm (3 in) trench mortar usabled for rapid fire on a surfaced submarine when caught. To act as minesweepers they also had two paravanes stowed on the structure’s walls but they were removed after completion to spare weight and complication as this feature was disused.
There were a few changes between batches:
The 1944 Ukuru group had their aft twin 120mm/45 10-shiki, and one aft 120mm/45 10-shiki forward, five triple 25mm/60 96-shiki, single 25mm/60 96-shiki (bridge) 81mm/12 ASW mortar forward, 12 DCT (120 depth charges), and a mechanical minesweeping gear.
The 1945 Yaku and Inagi groups had the same as above but five 25mm/60 96-shiki, still the 81mm/12 ASW mortar and 12 DCT (120) but no minesweeping gear.
1955: Those retained in JMSDF service from 1948 were stripped bare and retained a single 76mm/50 Mk 22, and two 20mm/70 Mk 10 for patrol and fishery guard work in Japanese waters. They were also fitted with a modern SO-3 radar.

12 cm/45 10-shiki (Type 10) naval gun

Instead of the venerable 12 cm/45 first designed in 1895 as a derivative of the Elswick Ordnance Pattern Y. It was from 1921 redesigned as an high-angle AA gun, called the 12 cm/45 10th Year Type. It had a Single motion interrupted screw Welin breech block different from the Type 3 12 cm AA Gun used by the Army in 1943. On destroyers it was always shielded with the latter fitted with two opening panels.
The ones fitted were not the 12 cm 11th Year Type naval gun (Model 1922) of TBs and the previous class, but the more advanced DP version found both on the Chidori and Etorofu class. It was said “dual-purpose” but in reality the mount limited them to 33° elevation only in the previous class, but this one might have the new HA mount that brought that elevation to 75° making for a maximum surface range of 22,430 yards (20,500 m) and a maximum AA Ceiling of 42,660 feet (13,000 m). Model 1922

⚙ specifications 12 cm/45 3rd Year

Weight 3,240 kg (7,140 lb), Barrel length 5.4 m (18 ft) bore
Elevation/Traverse -7° +75° and 120°/120°
Loading system: Welin breech block, Hydro-pneumatic recoil for 5–6 rpm
Muzzle velocity 825 m/s (2,710 ft/s), range 16 km (10 mi) at 33°
Crew: 6. Round 20.3 kg (45 lb) 120 x 550 mm.R., sep. loading cased charge

25 mm Type 96

These Type 96 25-millimeter (1 inches) anti-aircraft guns were placed in five triple-mount Type 96 25 mm abreast the bridge (2), abaft the smokestack (1), aft on the deck house (1) plus single-mount forward of the bridge and optionally two more located on the forecastle. The type 96 25 mm AT/AA gun became the standard of the IJA and IJN, automatic cannon developed as variant of the French Hotchkiss 25 mm, dual-purpose and developed as AA on single, twin and triple mounts. Development worked on 1935. 25 mm Hotchkiss design evaluated and order placed for several mounts types for evaluation at Yokosuka Naval Arsenal. Led to the Type 94 and Type 95 and then the main model produced at Yokosuka Arsenal, the Type 96. Elements made with castings and not forging for larger production, Rheinmetall supressor, new mounts designed. Air-cooled gas operated with multiple rings (Hotchkiss patent).

Twin-mount in 1939, followed by triple mount in 1941 and single mount in 1943. Issues of the designed revealed in combat:
Slow elevation and traverse, ineffective sights, excessive vibration, limited magazine cap., blinding Flashes.
The 1944 single mount needed a single operator and a loader but had a better spiderweb sight.

⚙ specifications 25 mm Type 96

Barrel Lenght 1.5 m (4 ft 11 in) L/60
Barrel weights: Single 785 kg (1,731 lb)
Barrel weights: Twin 1,100 kg (2,400 lb)
Barrel weights: Triple 1,800 kg (4,000 lb)
Crew: 3, 7 and 9 respectively
Shell 25×163mm
Exact caliber 25 mm (0.98 in)
Action Gas operated
Elevation/Traverse -10°/+85° – 360°, manual
Rate of fire 200–260 rpm (cyclic)
Muzzle velocity 820 m/s (2,700 ft/s)
Effective range 6.8 km (4.2 mi) at 45° with HE shell
Maximum firing range 85° 3 km (9,800 ft) effective, 5.5 km (18,000 ft) max.
Feed system 15-round box magazine

Depth Charges

The Mikura class were better armed against submarines, with still the same 81mm/12 Type 97 ASW mortar, but also no less than twelve Depht Charge Throwers for a grand total of 120 and a mechanical minesweeping gear. Initially these were Type 95 depth charges, with two Type 94 depth charge launchers.
Standard Type 95, 30.5″ by 17.7″ (77.5cm by 45cm). 220 lb (100 kg) charge, Type 88 explosive (ammonium perchlorate and ferrosilicate). Fuse using a water inlet. 100 feet (30m) and 200 feet (60m) settings (after the revelations of a US Congressman).
Later increased to 324 lb (147kg), Type 97 explosive (70% TNA/30% HNDA), 300 foot (90m) setting.
-1944 Type 2: 230 lbs (105kg) Type 97 explosive settings 98, 197, 292, 390, 480 feet (30m, 60m, 89m, 120m, and 145m).
-1945 Type 2: 357 lbs (162kg) explosives.

81mm Type 91 Mortar

A 15 cm (5.9″) ASW mortar was developed for transports and merchant ships in a cradle mounting that could fire a 60 lbs. (27 kg) charge at 4,500 yards (4,100 m) but it was too heavy for the esscorts, so instead, a modified Navy 81 mm mortar was carried by many escorts, firing standard projectiles. This modified version used by Imperial Japanese Navy with the designation Type 3 mortar was impromptu anti-submarine weapon designed for escort ships that was introduced in early 1943. This mortar was installed in front of the bridge and was some sort of “Japanese hedgehehog”.
The original Type 97 was a copy of the French Brandt mortar going back to 1936, produced from 1938 to the end of the war to 3892 units. It was fixed to the deck and weighted 66 kg (145 lb), but could fire at +85 degrees elevation a 6.5 kg (14 lb 5 oz) direct percussion charge at up to 1.2 km (0.75 mi). For longer range, they would use the Light HE: 3.3 kg (7 lb 4 oz) reaching 3 km (1.9 mi). Each of these were essentially grenades, to “clean up” the submarine deck from personal, especially gun crews. In theory it could also burst into the air or underwater at very short depth thanks to its delay pellet inserted in the fuze nose prior to firing.

Sensors

93-shiki (Type 93) sonar (1943)

2 kW 4400 lbs (2000 kg) model, FRQ 17.5 kHz, receiver gain 120 decibels 2, 4, or 8 seconds pulse interval, range up to 1640-3300-6600 yards (1500m-3000m-6000m) at 3°/10° resolution.
They also all kept their Type 93 Hydrophones in complement.

Type 3 Model 2 sonar

The Type 3 model 2 was an active echo-ranging sonar system utilized by the Imperial Japanese Navy during the later stages of World War II.Historical Overview & DevelopmentDeveloped as an evolution of the earlier Type 3 Model 1 active sonar (which itself was heavily based on German S-Gerät technology), the Model 2 was introduced around 1944–1945. It represented one of the IJN’s final attempts to upgrade their anti-submarine warfare (ASW) capabilities against the increasingly lethal Allied submarine fleet.DeploymentThe system was retrofitted or built directly into late-war escort vessels, and the first were installed on the Ukuru-class escort ships (Kaibokan).

These ships relied on the Type 3 Model 2 sonar in tandem with the Type 93 hydrophone to detect and track submarine targets. Unlike earlier variants, the Type 3 series introduced key technological refinements influenced by captured British equipment. These upgrades included Acoustic Improvements such as the incorporation of streamlined sound domes to reduce water resistance and self-noise while traveling. For data Recording it used chemical recorders to visually map and log echo ranges over time. Despite these updates, the late-war deployment was hampered by a lack of tactical doctrine for deep-water settings and resource scarcity, limiting its operational effectiveness during the final defense of Japanese shipping.

Type 22 Radar

The early Type 22 General Purpose Radar looks like characteristically like a 2910 lb (1320 kg) drum topped with a twin cornet amplificators, mounted mid-way top the mast.
Specs: Wavelength 10 cm, pwd 10 microsecond, PRF 2500 Hz, scan rate 5 rpm, PP 2 kW.
Range: 20 nautical miles (35 km) aircraft group, 10 nm (17 km) single, 13 nm(24 km) battleship.
Subject to land clutter. Horn and A scope display, accuracy 220 yards (200m)/3 degrees res. 1600 yards (1500 m)/40 degrees
300 sets produced installed on destroyers from the summer 1942. Generalized in 1944.

Type 13 Radar

Vertical 240 lb(110 kg) bedframe antenna, developed 1941, introduced mi-1943, with vertical dipole transmitter and Yagi mattress receiver. 1000 sets produced. Air defense, range 100 km (group), and single aircraft 50km. Specs: Wavelength 200 cm, pw 10 ms, PRF 500 Hz PP 10 kW, Range: 30-60 nautical miles (50-100 km).

E27 ECM suite

Electronic suite, installed in these ships from all groups. Officially designated as a “reverse-detection” system (Gyaku-Tan), it allowed Japanese vessels to intercept the radio and radar emissions of Allied forces. Its engineering design was heavily inspired by the German Metox receiver. With the Yanagi Missions, blueprints and prototype details for the Metox system were transferred to Japan by submarine. It worked as an early-warning indicator rather than an active jamming device. Detection capabilities spanning 75 cm to 400 cm. It was capable of identifying enemy radar or radio usage at distances up to 300 kilometres under optimal conditions. Weighing roughly 40 kg, it used a UN-955 receiver. Approximately 2,500 were manufactured, making it one of Japan’s most heavily produced electronic warfare system. Operational Deployment: Introduced from April 1944, E27 was quickly recognized and widely retrofitted across the fleet.

Modernization

By early 1945, surviving earlier ships had their minesweeping gear removed, traded for four additional 25mm/60 Type 96 AA guns. Those retained for cold service as frigates in 1955 like JDS Satsuma, Okija, Tsugaru, Atsumi, Kojima had this US pattern 76mm/50 Mk 22 aft under shield and two 20mm/70 Mk 10 Oerlikon guns. They were used until the 1960s for may roles, with clear markings, policing very extensive Japanese home waters and sites of whales fisheries.

Production (list and builders)

Tsurumi, Yokohama: Ukuru, Okinawa, Aguni, Amami.
Uraga, Tokyo: Shinnan, Chikubu, Kozu, Hodaka, Ikara, Ikino, Urumi, Murotsu
Mitsui, Tamano: Inagi, Habushi, Oga, Kanawa, Takane
Hitachi Sakurajima: Hiburi, Shonan, Daito, Kume, Ikuna, Mokuto, Sakito, Habuto, Shisaka, Otsu
Sakurajima, Osaka: Tomoshiri.
Sasebo K K: Uku, Kuga, Shiga.
Maizuru K K: Iwo
Ukuru (#332), Okinawa (#335), Amami (#336), Aguni (#337) and Shinnan (#338) were altered to the Ukuru design.

⚙ Ukuru class specifications
Displacement	940t standard, 1020t FL
Dimensions	77.7 x 9.1 x 3.05 m (255 ft x 29 ft 10 in x 10 ft)
Propulsion	2 shafts geared Kampon diesel (4,200 bhp)
Speed	19.7 knots (22.7 mph; 36.5 km/h)
Range	5,000 nautical miles at 16 knots
Armament	2×1, 1×1 120m/45 Type 10, 5×3 25mm/60 Type 96, 1-6 single, 81mm/12 ASW mortar, 12 DCT (120), sweeping gear
Sensors	Type 22 radar, Type 93 sonar, see notes
Crew	150 (1945)

Gallery

Irootoko’s colorized gems

IJN Sionan

IJN Daito

IJN Yaku

IJN Shisaka

Creative Commons

IJN Amami 1945

Japanese ocean station vessel Ukuru Maru c1948

Japanese escort ship Ukuru launching ceremony

IJN escort vessel UKU 1944

Japanese escort ship Shinnan as minesweeper tender 1946

Japan’s Petroleum Development Corporation barracks ship Tsugaru

Japanese escort ship Shinnan 1944

Japanese escort ship Kanawa postwar

Japan Coast Guard PL104 Satsuma

A preserved Shiga as of 2022

Career of the Ukuru class

Note: Ukuru below is the only extensive career detailed for now as an example. There should be an update for others in 2027.

IJN Ukuru (鵜来) (1944)

Ordered under hull number #332, IJN Ukuru was laid down at Nihon Kōkan, Tsurumi on 9 October 1943, launched on 15 May 1944 and commissioned on 31 July 1944. She was registered in the Sasebo Naval District and attached to the Kure Guard Unit under command of Res. LtCdr Kuwahara Tadao (on CH-33 sub-hunter prior to that) for the final fitting out at Saeki. On 5 August 1944 in the morning she departed Tsurumi for Yokosuka and worked up for 6 weeks. On 19 September she left Yokosuka for Takeoka, then Irako a day later, Tokuyama, Saiki (23st). She stayed there for mission preparations, and departs on 11 October for Uzuki Bay, Saiki, Sasebo (14th) to be assigned 2 days later at the General Escort Command’s First Surface Escort Division. She sailed to Moji from Sasebo and on the 26st left for Singapore with the light cruiser Kashii in the lead as flasghip, Rear Admiral Yoshitomi Setsuzo for the 5th Escort Group, as well as IJN Nomi, the minelayer Niizaki and convoy HI-79 (5 freighters and the fleet supply ship MAMIYA). CD-17 later joins the escort, then the minesweeper W-21 joins but on the 29st UKURU and CD-17 are detached to escort MELBOURNE MARU to Kirun, and back to the convoy.
On the 30st she drops anchor off Takao and departs the following day. While underway on 2 November east of Hainan at 14:32, the convoy is bombed by a lone Consolidated B-24 “Liberator” heavy bomber from high altitude, missed. On 8 November ARIMASAN MARU has an engine breakdown but they all arrives off Singapore and departs a on 15 November. Ukuru is assigned to the 101st Escort Squadron still under orders from IJN Kashii but now with her sister Daito and two other vessels, W21 and CD-17.

On 17 November 1944 she departs Singapore with her sister Manju, ahd half-sisters Nomi, Kasado, Miyake, CD-17 and CD-51, Niizaki and convoy HI-80 (8 merchant ships). On the 20st, CD-23 joins them off Cape St Jacques in place of CD-17 detached to Saigon. On the 27th, two are detached for Takao. On 2 December they arrives at Imari Bay, drops anchor a day later at Mutsure and UKURU is detached. The convoys arroves on 4 December at Sasebo. Ten day later, Ukuru returns to Mutsure. She departed on the 15th for Himejima, Moji and on the 19st she takes part in convoy HI-85 (2 tankers + convoy MOTA-38 with the Army landing ship carriers HYUGA, KIBITSU and SHINSHU MARU, 5 Army transports) via Takao on the 23rd. On the 27th, they depart for Singapore and on the 29st they are joined by W-101. On 30-31 December they are attacks sporadically by marauding B-24s (or PB4Y-2 Privateers as they looked alike from below). On 1 January 1945 they arrives at Qui Nhon Bay, then Nha Trang Bay, and later underway in the Hainan Straits, they are attack by a PB4Y (this time correctly identified and indeed frequenty deployed alone) from astern, gliding while engines cut for surprise. One bomb hits TEIHOKU MAR, last ship in the west column (ex-French PERSEE), detached to Yulin for repairs. TSUSHIMA is damaged by a near miss later. On the 4th convoy HI-85 arrives at Cape St. Jacques, then Saigon to be dissolved.
On 6 January Ukuru left Saigon for St Jacques, then Moji with the same combat group headed by Kashii, her sister Daito and three sub-chasers. Convoy HI-86 comprises only tankers bound for Japan. On the 11st they transit by Ban Phong Bay, then Qui Nhon Bay. However the agenda was bad. On 12 January the US launches Operation “Gratitude” a massive strike by TF 38 on Indochina. From 11:00 to 17:00 they are spotted and unreletless attacks from Curtiss SB2C Helldiver dive-bombers and Grumann TBF Avenger torpedo-bombers from T. Sherman’s USNA 17 USS ESSEX (CV-9), TICONDEROGA (CV-14), LANGLEY (CVL-27) and SAN JACINTO (CVL-30). The result: YOSHU and EIMAN MARUs, CD-23 and CD-51 are sunk, the fleet tanker SAN LUIS MARU, UKURU are in flames, badly damaged, as well as IJN Daito and CD-27. Others are so badly damaged they have to be beached: OTSUSAN, TATEBE, YUSEI, TATSUBATO MARUs, BANSHU MARU No. 63 (later constructive total losses). Kashii is also hit starboard amidships by a torpedo then a pair of SB2C hits aft, setting off her depth charge magazine, and blowing up her entire aft section, so she sank with 621 sailors, 19 rescued. The convoy, loaded with critical material for the Japanese industry, has been wiped out.
Convoy HI-86’s head, Rear Admiral Shibuya Shiro is among the dead, promoted Vice Admiral posthumously. Ukuru also tries to save men for the cruiser but at 14:30 the air attack resumes and she leave at full speed with only 19 men on board, condemning the remainder to the sharks and drowning by fatigue or hypothermia. She managed to escape all attacks by maneuvering jard rudder and finding rain squalls. Herself due to near-misses and shrapnels had 12 dead in her crew and 29 injured.
On 13 January she manages to reach Samah (Sana), then Yulin and together with Daito and CD-27 she managed to take shelter in Hainan Island. On this is short: On the 15th, they are spotted by the vanguard of TF 38 off Yulin, and between 11:00 and 12:40 attacked again. This time, the tanker HARIMA MARU goes down and Daito is damaged again. The others taks protection along the shore near the mountains and claims a F4U Corsair from USS ESSEX. On the 16th, they are attacked again by 30-40 Helldiver and F6F hellcats loaded with rockets attacking shore targets but damaged to the escorts or freighters is light.
On the 17th there was another such attack, same results. On 21 January Ukuru and the escort force leaved Yulin for Moji and anchored off Basuo then northeast Hainan Island on on the 23st there was a night attack by a PB4Y on TSUSHIMA (near miss). At 0930, they are attacked by another but their position is known. On the 26 January 1945 she arrives at Nanji Tao with the Army landing ship carrier KIBITSU MARU.
On the 27th, she departs Nanji Tao for Ssu Chiao Shan then Seito (Tsingtao). On 6 February she departs for Moji, then Daito Wan, Kogunsan Gunto, Kyosai To (Koje Island) and back to Moji in patrol. On 11 February she left Moji for Imari Bay to Sasebo, drydocked for repairs until March. She is then reassiged to convoys, this time between Japan and Shanghai or Tsingtao.
On 8 March LtCdr Kuwabara is replaced by Res. LtCdr Shimada Suetsugu and she departs Sasebo for Mutsure, Moji and still with IJN Daito, repaired and rearmed, she escorts the convoy MOSHI-01 with ABUKUMAGAWA MARU and they arrive on 15 March at Shanghai. They left on the 18th with CD-27 and SHIMO-01 (4 ships) for Katoku Suido (23rd) then Chinkai and later meet the Hosho Maru convoy with CHa-27, relieving CD-8, CD-32 and CD-52 in need of refuelling. On the 25th, she is reassigned to the First Escort Fleet and arrives at Kokusan Gunto in Chosen.
On the 26th she left for Yulin (2 April) and a day later left Amoy with HOMO-04 convoy (MANSHU MARU, SONJO MARU) for Shanghai. On the 10th they are attacked by USAAF or Chinese Airforce planes. MANSHU MARU is badly damaged by bombing and SONJO MARU suffers light damage from strafing or near misses. SONJO MARU continues the voyage. It is unclear what escorts accompanied the ship there or remained with MANSHU MARU. MANSHU MARU later apparently proceeds to Mutsure.
On 20 April 1945 she left Shanghai for Maizuru but two ddays later while underway thet are attacked by ten Consolidated B-24 Liberator (no hits). One bomber is damaged, ditched later. The convoy arrives at Tsingtao and on the 25th arrives at Chinkai, Korea. UKURU and DAITO are reassigned to Captain Abe Tokuma and his 22nd Coast Defense Group.
On 8 May SW of Mokpo (Korea) underway to Japan, KOTOBUKI MARU hits a mine from a B-29 but survives, and managed to reach Maizuru under tow. Ukuru remains there without assignement due to the lack of fuel. On 22 July IJN Kashima takes the lead of a new escort group with Chikubu and Takane, and they left Maizuru. On 15 August while off Ominato, Honshu, Ukuru is underway from Akita to Ominato when radioed about the end of the war. On the 23st she arrives at Sasebo, on the 30th she is stricken, from the lists, sekelton crew disbanded.
On 1st December she is converted as a minesweeper by Allied Forces and mostly disarmed. On 10 July 1946 she acts as minesweeper tender. On 2 December 1947 she is stricken again, mothballed. On 26 December she is transferred to the Japanese Maritime Transport Bureau and converted as a Central Meteorological Observatory weather survey ship, renamed UKURU MARU. She takes part in the summer season typhoon patrols with Chibuku, Ikuna and Shionan Marus. On 1st January 1954 she is transferred to the Japanese Maritime Safety Agency as a patrol ship, renamed SATSUMA (PL-104). She is used to patrol Japanese fishery areas against Chinese and Russian trawlers. She is sold for scrapping on 24 November 1965.

IJN Okinawa (沖縄) (1944)

Ordered under hull number #335, IJN Okinawa was laid down at Nihon Kokan, Tsurumi on 10 December 1943, launched on 19 June 1944 and commissioned on 16 August 1944. Okinawa was damaged by a bomb in an air attack by P-38s while escorting TA no. 2 on 5 November 1944 and damaged by PT boats on 9 November and by aircraft again on 18 November 1944. Okinawa was sunk on 30 July 1945 by aircraft from HMS Formidable.

IJN Amami (奄美) (1944)

Ordered under hull number #336 IJN Amami was laid down at Nihon Kokan, Tsurumi on 14 February 1944, launched on 30 November 1944 and commissioned on 8 April 1945. Amami survived the war and was ceded to the UK as a war reparation and scrapped on 20 December 1947.

IJN Aguni (粟国) (1944)

Ordered under hull number #337 IJN Aguni was laid down at Nihon Kokan, Tsurumi on 15 February 1944 21 September 1944, launched on 2 December 1944 and commissioned on 27 May 1945, Aguni was damaged by a Bat glide bomb. The bomb’s 1,000 lb (450 kg) warhead exploded off Aguni’s starboard bow demolishing the whole foredeck area ahead of the bridge and killing 33 sailors. After being hit, Aguni’s crew had to cut her anchor chain to free her. Kaibokan CD-12 was dispatched to assist Okinawa in rescuing Aguni’s crew, but despite the heavy damage the kaibokan remained navigable and proceeded stern first to Pusan, Korea on her own power. Aguni survived the war and was sold for scrapping on 20 May 1948.

IJN Shinnan (新南) (1944)

Ordered under hull number #338 IJN Shinnan was laid down at Uraga Dock Company on 30 June 1944, launched on 4 September 1944, and commissioned on 21 October 1944. Shinnan survived the war and later became a weather survey ship in the Japanese Maritime Transport Bureau before being sent to the petrol development agency in October 1967. She was scrapped in 1975.

IJN Shōnan (昭南) (1944)

Ordered under hull number #339 IJN Shōnan was laid down at Hitachi Zōsen, Sakurajima on 23 February 1944, launched on 19 May 1944 and commissioned on 13 July 1944. Torpedoed and sunk by USS Hoe on 25 February 1945, with 198 crew and passengers killed.

IJN Inagi (稲木) (1944)

Ordered under hull number #4701 Inagi was laid down at Mitsui Shipbuilding & Eng., Tamano on 15 May 1944, launched on 25 September 1944 and commissioned on 16 December 1944. Inagi was bombed and sunk by planes from HMS Formidable on 9 August 1945, with the loss of 29 killed and 35 wounded.

IJN Habushi (羽節) (1944)

Ordered under hull number #4702 IJN Habushi was laid down at Mitsui Shipbuilding & Eng., Tamano on 20 August 1944, launched on 20 November 1944 and commissioned on 10 January 1945. Habushi struck a mine on 8 April 1945 and was damaged. She survived the war and was ceded to the United States as a war reparation and scrapped starting 17 October 1947.

IJN Ojika (男鹿) (1944)

Ordered under hull number #4703 IJN Ojika was laid down at Mitsui Shipbuilding & Eng., Tamano on 7 September 1944, launched on 30 December 1944 and commissioned on 21 February 1945. Ojika was torpedoed and sunk by USS Springer on 2 June 1945.

IJN Kanawa (金輪) (1944)

Ordered under hull number #4704 IJN Kanawa was laid down at Mitsui Shipbuilding & Eng., Tamano on 15 November 1944, launched on 20 January 1945, commissioned on 25 March 1945. Kanawa survived the war and was ceded to the UK as a war reparation and scrapped on 14 August 1947.

IJN Uku (宇久) (1944)

Ordered under hull number #4705 IJN Uku was laid down at Sasebo Naval Arsenal on 1 August 1944 12 November 1944 and commissioned on 30 December 1944. Uku struck a mine on 9 April 1945 and was damaged. She survived the war and was ceded to the United States as a war reparation and later scrapped.

IJN Takane (高根) (1945)

Ordered under hull number #4707 IJN Takane was laid down at Mitsui Shipbuilding & Eng., Tamano on 15 December 1944, launched on 13 February 1945 and commissioned on 26 April 1945. Takane survived the war and was scrapped starting 27 November 1947.

IJN Kuga (久賀) (1944)

Ordered under hull number #4709 IJN Kuga was laid down at Sasebo Navy Yard on 1 August 1944, launched on 19 November 1944 and commissioned on 25 January 1945. Kuga struck a mine on 25 June 1945 and was damaged. She survived the war and was scrapped on 30 June 1947.

IJN Shiga (志賀) (1944)

Ordered under hull number #4711 IJN Shiga was laid down at Sasebo Naval Arsenal on 25 November 1944, launched on 9 February 1945 and commissioned on 20 March 1945. Shiga survived the war and later became a weather survey ship in the Japanese Maritime Transport Bureau before being discarded on May 6, 1964. Her hull became the pavilion for Maritime Amusement Park in Chiba City, but her hull deteriorated because of poor maintenance and was dismantled and scrapped in 1998.

IJN Iwo (伊王) (1944)

Ordered under hull number #4712 IJN Iwō was laid down at Maizuru Naval Arsenal on 25 November 1944, launched on 12 February 1945 and and commissioned on 24 March 1945. Iwo struck a mine on 13 June 1945 and was damaged. She was damaged lightly in an air attack by planes from USS Shangri-La, losing 4 killed and 61 wounded. She survived the war and was scrapped starting 2 July 1948.

IJN Yaku (屋久) (1944)

Ordered under hull number #5251 IJN Yaku was laid down at Uraga Dock Company on 30 June 1944, launched on 4 September 1944 and commissioned on 23 October 1944. Torpedoed and sunk by USS Hammerhead on 23 February 1945, with the loss of 132 men.

IJN Kume (久米) (1944)

Ordered under hull number #5252 IJN Kume was laid down at Hitachi Zōsen, Sakurajima on 26 May 1944, launched on 15 August 1944 and commissioned on 25 September 1944. Torpedoed and sunk by USS Spadefish on 28 January 1945, with the loss of 89 men.

IJN Chikubu (竹生) (1944)

Ordered under hull number #5253 IJN Chikubu was laid down at Uraga Dock Company on 8 September 1944, launched on 12 November 1944 and commissioned on 31 December 1944. Chikubu survived the war and later became a weather survey ship in the Japanese Maritime Transport Bureau before being sold for scrapping on 4 October 1962.

IJN Ikuna (生名) (1944)

Ordered under hull number #5254 Ikuna was laid down at Hitachi Zōsen, Sakurajima on 30 June 1944, launched on 4 September 1944, completed on 15 October 1944 and commissioned on Ikuna was hit by a torpedo by USS Crevalle and damaged on 10 April 1945. On 1 August she struck a mine and was damaged. Ikuna survived the war and later became a weather survey ship in the Japanese Maritime Transport Bureau before being sold for scrapping on 25 May 1963.

IJN Kōzu (神津) (1944)

Ordered under hull number #5255 IJN Kōzu was laid down at Uraga Dock Company on 20 October 1944, launched on 31 December 1944 and commissioned on 7 February 1945. She survived the war and was ceded to the Soviet Union as a war reparation on 28 August 1947. Served in Soviet Pacific Ocean Fleet as patrol ship EK-47 (1947), oceanographic research ship Nord (1948), later – Glubomer (1953), repair ship PM-62 (1955). Decommissioned on 25 January 1969 and scrapped.

IJN Hodaka (保高) (1945)

Ordered under hull number #5256 IJN Hodaka was laid down at Uraga Dock Company on 27 November 1944, launched on 28 January 1945 and commissioned on 30 March 1945. She survived the war and was ceded to the United States as a war reparation and scrapped starting 1 March 1948.

IJN Shisaka (四阪) (1944)

Ordered under hull number #5257 IJN Shisaka was laid down at Hitachi Zōsen, Sakurajima on 21 August 1944, launched on 31 October 1944 and commissioned on 15 December 1944. She survived the war and was ceded to the Republic of China Navy as a war reparation and renamed as Huai An (惠安), but later was captured by the Chinese communists at the end of Chinese Civil War, and entered PLAN under the same name. The ship was later renamed as Rui Jin (瑞金) and served as a training ship in PLAN until the early 1980s before it as finally scrapped.

IJN Ikara (伊唐) (1945)

Ordered under hull number #5258 IJN Ikara was laid down at Uraga Dock Company on 26 December 1944, launched on 22 February 1945 and commissioned on 30 April 1945. On 9 August 1945, Ikara struck a mine and sank.

IJN Sakito (崎戸) (1945)

Ordered under hull number #5259 IJN Sakito was laid down at Hitachi Zōsen, Sakurajima on 7 September 1944, launched on 29 November 1944 and commissioned on 10 January 1945. On 27 June 1945, Sakito struck a mine and was damaged. Sakito survived the war and was scrapped on 1 December 1947.

IJN Ikuno (生野) (1945)

Ordered under hull number #5260 IJN Ikuno was laid down at Uraga Dock Company on 3 January 1945, launched on 11 March 1945 and commissioned on 17 July 1945. She survived the war and was ceded to the Soviet Union as a war reparation on 29 July 1947. Served in Soviet Pacific Ocean Fleet as patrol ship EK-41 (1947), target ship TsL-41 (1948), oceanographic research ship Val (1949). Decommissioned on 1 June 1961 and scrapped.

IJN Mokuto (目斗) (1945)

Ordered under hull number #5263 IJN Mokuto was laid down at Hitachi Zōsen, Sakurajima on 5 November 1944, launched on 7 January 1945 and commissioned on 19 February 1945. On 4 April 1945, Mokuto struck a mine and sank.

IJN Habuto (波太) (1945)

Ordered under hull number #5264 IJN Habuto was laid down at Hitachi Zōsen, Sakurajima on 3 December 1944, launched on 28 February 1945 and commissioned on 7 April 1945. Habuto struck a mine on 6 June 1945 and was damaged. She struck a second mine on 10 June 1945 and was again damaged. She survived the war and was ceded to the UK as a war reparation and scrapped on 16 July 1947.