This was the Japanese naval undertaking to bring the two hybrid battleship/aircraft carrier conversions of the ‘Ise’ class, together with four escort ships, back from Singapore to Japanese home waters (10/20 February 1945).
With their two after turrets removed to allow the addition of a hangar and small flight deck, each of these 1943 conversions had a notional provision for 22 aircraft. Hyuga and Ise had been based at Singapore since November 1944, and while their movement back to Japan was detected by the Allies, all attempts to make effective submarine and aircraft attacks failed. As a result of the intensifying Allied air and sea blockade of the Japanese home islands, the two ‘Ise’ class battleship/carriers and their escorts were among the last Japanese warships to reach the home islands from the South-West Pacific before the end of the war.
During 1944, Allied submarine attacks had effectively cut off the supply of oil to Japan from the South-East Asian oilfields and refineries, and greatly reduced Japanese imports of other commodities. By this stage of the war, Japan’s oil reserves had been largely exhausted. At the same time US submarines sank many Japanese warships, these including the battleship Kongo, seven aircraft carriers, and two heavy and seven light cruisers. Early in 1945, the Japanese assessed that all convoy routes from the south would eventually be cut, and attempted to supplement the supplies of oil delivered in bulk by dedicated tankers by loading drums of oil on freighters, and several aircraft carriers were also used to transport drums of oil from Singapore to Japan.
On 11 November 1944, Ise and Hyuga, which constituted Rear Admiral Matsuda Chiaki’s 4th Carrier Division, departed the home islands to join the Japanese navy’s surviving main strength in the South-West Pacific. This deployment had the double purpose of reinforcing the remaining elements of the Japanese navy in the area and of basing the ships near a source of fuel. During their voyage from Japan, each of the battleship/carriers was loaded with about 900 tons of munitions for the units defending Manila in the Philippine islands group. As a result of heavy Allied air attacks on Manila, the two warships unloaded their supplies in the Spratly islands group from 14 November, and then departed for Lingga Roads near Singapore on 20 November and reached their destination on 22 November. The Allies already knew of the movement of the ships, and though ordered to keep watch for the ships, Allied submarines did intercept neither Ise nor Hyuga during the two ships' passage to Singapore. The ships were deployed to Cam Ranh Bay in Indo-China during December and returned to Singapore on 11 January 1945.
Warships of Admiral William F. Halsey’s US 3rd Fleet raided the South China Sea between 10 and 20 January in search of the Japanese fleet, but did not find the two ships. Early in February, Ise, Hyuga and an escort of smaller warships received orders to sail to Japan in ‘Kita’, the accompanying warships being the light cruiser Oyodo, which became part of the 4th Carrier Division on 10 February, and the destroyers Asashimo, Hatsushima and Kasumi.
The ships of what was now designated the Completion Force steamed from the Lingga Roads on 6 February and began loading their cargoes in Singapore on the following day. Shortly before docking, Ise sustained modest damage when she struck an air-laid Allied mine. During the Completion Force’s stay at Singapore, its six ships were loaded with supplies and Ise received temporary repairs. Hyuga took on board 4,944 drums of aircraft fuel as well as 326 drums of motor fuel and 440 oil field workers. Ise was loaded with 5,200 drums of aircraft fuel and 551 oil workers: each of the battleship/carriers also embarked 1,560 tons of rubber, 1,560 tons of tin and 178.5 tons of other metals. Oyodo was loaded with 107 tons of tin, 62.5 tons of tungsten, 70 tons of aircraft fuel, 44.6 tons of rubber, 35.7 tons of zinc and 17.85 tons of mercury. Some 125 more tons of rubber and tin were divided among the three destroyers.
Allied intelligence was aware of the Completion Force’s composition and objectives as a result of careful monitoring and decryption of radio traffic in the Singapore region, and the ‘Ultra’ intelligence which resulted provided details of the two capital ships’ movement to Singapore, preparation for return to Japan, and even the ships’ planned route.
The commander of Task Force 71, the Allied submarine forces in the South-West Pacific Area, was Rear Admiral James Fife, who placed a high priority on preventing the return of Ise and Hyuga to Japan. Fife therefore stationed 15 submarines along the Japanese ships’ expected route. A plan for co-ordinated attacks on the ships by the US Navy and USAAF was also developed. At the time, Vice Admiral Thomas C. Kincaid’s US 7th Fleet had four battleships (Colorado, Mississippi, Pennsylvania and West Virginia) in Filipino waters to guard the Allied ‘Mike I’ beach-head at Lingayen Gulf in Luzon against attacks by the Japanese forces based at Lingga Roads and the Inland Sea until the USAAF forces in the region were strong enough to assume this responsibility. As of a time early in February, the USAAF units in the Philippine islands group were focused on supporting the US Army-led Philippines campaign and attacking Japanese facilities in Formosa. An intensive campaign against Japanese shipping in the South China Sea had been planned, but had yet to be started.
The Completion Force departed Singapore during the evening of 10 February, this timing being determined by a long-term forecast of bad weather for the voyage to Japan. The British submarine Tantalus observed the ships leaving port and attempted to attack them on 11 February, but was driven off by a Japanese aeroplane. Following this action, Tantalus radioed a contact report to Fife’s headquarters. Meanwhile the four US battleships at Lingayen Gulf departed on 10 February for US bases in the Pacific where they were to receive repairs and undertake preparations ahead of their role supporting the ‘Iceberg’ invasion of Okinawa, and these capital ships left the area of the Philippines islands group on 14 February without having played any part in efforts to intercept the Completion Force.
US submarines attempted unsuccessfully to attack the Japanese ships on 12 February. At about 13.45, Charr detected the Completion Force at a distance of 9 miles (143.5 km) on radar and transmitted a contact report, one hour later Blackfin made radar contact with the Japanese ships at a range of 15 miles (24 km), and during the next 14 hours the submarines Blackfin, Charr, Flounder, Pargo and Tuna attempted to reach a position in which they could attack the Japanese ships, but were unable to do so. Another group of US submarines (Guavina, Hake and Pampanito) farther to the north was also unable to reach a position in which the boats could attack the Completion Force.
USAAF patrols made contact with the Completion Force on 12 February, and after this the Japanese ships were tracked almost continuously by radar-equipped by USAAF and US Navy aircraft. On the morning of 13 February, a force of Consolidated B-24 Liberator heavy bombers and 40 North American B-25 Mitchell medium bombers escorted by 48 North American P-51 Mustang fighters was despatched from several bases on Leyte and Mindoro islands in the Philippines islands group to attack the Japanese ships. While the aircraft successfully rendezvoused near the Completion Force, heavy cloud cover kept them from spotting any of the ships. As radar-directed blind bombing was prohibited to avoid accidental attacks on the Allied submarines in the area, the bombers returned to their bases without attacking.
On the same day, the Australian destroyers Arunta and Warramunga departed Lingayen Gulf and proceeded to a position about 300 miles (480 km) to the west of Manila, where they were held in readiness to rescue the crews of any aircraft downed while attacking the Completion Force. The two Australian destroyers were released for other duties on 15 February.
More submarines attempted to attack the Japanese force on 13 February. A group of three boats (Bergall, Blower and Guitarro) was deployed along the route of the Japanese ships, and Bergall sighted the ships at 12.30. The submarine was submerged at the time and attempted to manoeuvre into a firing position, but could get no closer to the ships than 4,800 yards (4390 m). Nevertheless, the boat fired six torpedoes, all of which missed. Blower attempted a submerged attack, but the five torpedoes it fired at one of the battleship/carriers and Oyodo missed. Bashaw and Flasher, the northernmost of the submarines which Fife had deployed, encountered the Completion Force during the afternoon of 13 February. Bashaw sighted the Japanese ships as they emerged from a rain squall at 15.15, but one of the battleship/carriers spotted the submarine and launched an aeroplane to attack it. Bashaw was forced to dive when the battleship/carrier began shelling the boat with its main battery, and neither Bashaw nor Flasher was able to intercept the Completion Force.
During this period the other submarines in the area continued to chase the Japanese ships, but did not regain contact with them. An air attack was attempted against the Completion Force on 14 February. The number of B-24, B-25 and P-51 aircraft despatched on this day was smaller than the force which had been used on 13 February, as the Japanese ships were now beyond the range of aircraft based on Leyte. Once again, cloud cover over the Completion Force prevented the US aircraft from sighting the Japanese ships, and they were not permitted to attack as a result of the prohibition on radar-aimed bombing. This was the USAAF’s last attempt to bomb the Japanese force. As a result, the only successes gained by the USAAF aircraft involved in the operation were the shooting down of a Mitsubishi Ki-57 ‘Topsy’ transport aeroplane near the Completion Force on 13 February as well as several fighters in the area of the ships between 12 and 14 February.
Vice Admiral Charles A. Lockwood, the commander of the US Pacific Fleet’s submarine force, followed the unsuccessful attempts to intercept the Completion Force in the South China Sea, and stationed another 11 boats along the Japanese ships’ projected route between the Luzon Strait and Japan. The Completion Force reached the Matsu islands group at the northern end of the Formosa Strait during the evening of 15 February, and anchored there for five hours before resuming its passage to Kure via Pusan in Korea and the Shimonoseki Strait at 24.00, and the destroyers Kamikaze and Nokaze were attached to the force for part of the day.
At 05.07 on 16 February, the US submarine Rasher intercepted the Completion Force to the south of the Chinese port city of Wenchow and fired six torpedoes at one of the escorts, but all of these missed. At this time the Japanese ships were steaming at 18 kt. None of the other US submarines made contact with the Japanese force as it sailed to the east of where they had been positioned by Lockwood.
The Completion Force finished its voyage toward the end of February. It anchored off Chusan island near Shanghai from 9.06 on 16 February until 07.00 on 18 February, when it sailed for Sanzenpo harbour near Sacheon on the south coast of Korea. It arrived there at 16.00 on the same day, and anchored overnight. The Completion Force departed Sanzenpo harbour at 07.00 on 19 February and reached the Japanese island of Mutsurejima at 04.00 on the same day. After anchoring overnight, the Completion Force docked at Kure at 10.00 on 20 February. The ships of the Completion Force were among the last Japanese warships to reach the home islands from the South-West Pacific.
The Allied naval commanders were highly disappointed by the failure of the 26 submarines directed against the Completion Force to inflict any damage on the ships. Fife concluded that this was a result of the Completion Force’s high speed, the poor weather conditions at the time of the operation, and the presence on the Japanese ships of equipment to detect the submarines’ radar transmissions.
The use of freighters and warships to carry oil was successful in increasing Japanese oil imports, and the total level quality of oil which reached the country during the first quarter of 1945 was greater than the amounts achieved late in 1944. Even so, Allied submarines sank the majority of the merchant tankers that attempted to sail from South-East Asia to Japan during February, and in March the Japanese ceased attempting to import oil from this source. Following the departure of the Completion Force, the only major seaworthy Japanese warships remaining in the South-West Pacific were the heavy cruisers Ashigara and Haguro as well as the light cruiser Isuzu. These three cruisers did not attempt to return to Japan, and all were sunk by Allied submarines and destroyers between April and June.
After reaching Japan, Ise and Hyuga were assigned to bolster the anti-aircraft defences of the city of Kure and its naval base. For lack of fuel and aircraft, the ships did not put to sea again, and both were sunk during the US Navy’s attacks on Kure between 24 and 28 July. Oyodo became part of the Kure Training Force and remained in port until she was sunk on 28 July. The three destroyers were also sunk: Asashimo and Kasumi fell victim to US carrierborne aircraft while escorting the super-battleship Yamato during ‘Ten’ on 6 April, and Hatsushima sank after striking a mine near Maizuru on 30 July.