Operation Raids on Jaluit, Wotje, Maloelap and Mili Atolls

The 'Raids on Jaluit, Wotje, Maloelap and Mili Atolls' were surface ship and air attacks by US forces on a quartet of atolls in the Japanese-held Marshall islands group of the central Pacific Ocean (1 February 1942/15 August 1945).

After World War I, Japan had received a mandate from the League of Nations to administer the Marshall islands group, which the Japanese had taken from the Germans in that war.

The Marshall island group comprises five islands and 29 coral atolls, comprising 1,156 individual islands and islets in two primary chains. These are the Ralik and Radak chains in the group’s western and eastern parts. Jaluit atoll is located near the southern end of the Ralik group, and its nearest neighbour is Kili island about 30 miles (48 km) to the south-west, with Kwajalein atoll 245 miles (395 km) to the north-west and Majuro atoll about 110 miles (177 km) to the north-east.

Wotje and Maloelap atolls lie in the central portion of the Radak group while Mili atoll is at the southern end of the group. Majuro atoll is situated between Maloelap 98 miles (158 km) to the north, and Mili 65 miles (105 km) to the south-east. Wotje is 164 miles (264 km) to the east of Kwajalein, Maloelap is 70 miles (113 km) to the south-west of Wotje, and Mili is 165 miles (266 km) to the south-south-east of Wotje. Some 145 miles (233 km) due east of Mili is Jaluit. Wotje is considered a part of the Romanzow group along with the small Erikub atoll to the south and a few scattered islands between the two atolls. These four atolls are similar to others in the Marshall islands group in being of roughly oval shape with numerous low islands and islets surrounding a lagoon. The islands are covered with palms, pandanus trees and salt brush.

Jaluit is about 12 miles (19.3 km) across its broader southern end from East to West Points, but only 4 miles (6.4 km) wide at its northern end, and almost 30 miles (48 km) long from west-north-west to east-south-east. Of its 50 islands, the largest is the long, narrow, L-shaped (with an extremely long vertical arm) Jaluit island. Jabur island was the Japanese administrative centre of the Marshall islands mandate, and on this island the Japanese developed a major naval base exploiting the advantages offered by its deep and well-protected lagoon, which had the area to accommodate 1,500 ships, and could be accessed by four passes up to 55 ft (16.75 m) deep. However, Jaluit suitability for the development of a major naval base was reduced by the lack of sufficient for the construction of an airfield capable of supporting military aircraft. Before the outbreak of the Pacific War, the Japanese established Imiage naval seaplane base on the atoll’s south-eastern rim, with a few seaplanes (four Mitsubishi F1M2 'Pete' single-engined observation floatplanes and two Aichi E13A 'Jake' single-engined reconnaissance floatplanes) and one squadron of 11 Kawanishi H6K 'Mavis' four-engined flying boats of the Yokohama Kokutai. The atoll was garrisoned by the 51st Guard Force just before war broke out. However, the Japanese did little further development of the base other than the creation of small installations on Emidj and Enybor islands to the north of Jaluit.

Jaluit was the primary target of Rear Admiral Frank J. Fletcher’s Task Force 17 (centred on the fleet carrier Yorktown) during its raid on the Marshall islands group on 1 February 1942. The aircraft despatched to attack Jaluit met appalling weather, however, and several aircraft never found the target; the aircraft which did find Jaluit inflicted only light damage on the 8,900-ton transport vessel Kanto Maru.

Jaluit was bypassed by the Kwajalein invasion of December 1944, and an air mining attack on 4 January 1945 led the Japanese to close the base permanently.

Wotje atoll is 30 miles (48 km) long from east to west and 8 to 12 miles (12.9 and 19.3 km) wide. Most of its Wotje’s 65 islands lie along its eastern rim, where the largest islands are located, and its central southern side; a few islands are scattered along the north western side. The largest island is Wotje itself on the extreme eastern central end. Wotje’s capacious lagoon had room for 2,000 ships, and could be reached by four passes, the most significant of which had a depth of 90 ft (27.5 m). The island also had enough land area for an airfield, making it an excellent candidate for development as a naval base, and by 1941 the Japanese had constructed perhaps their strongest base in the Marshall islands group, with 3,445-ft (1050-m) and 4,920-ft (1500-m) runways at Otdia air base, but no aircraft had yet based there when the Pacific War broke out. There was also a seaplane base, numerous anti-aircraft and coastal artillery batteries, and a system of roads and trenches. The atoll was garrisoned by the 53rd Guard Force, which arrived just before the outbreak of war.

The atoll was bombarded by a US cruiser force under Rear Admiral Raymond A. Spruance on 1 February 1942 and then by a US battleship force on 29 January 1944 during the Marshall islands campaign. Thereafter the atoll was bypassed, and though it was repeatedly bombarded by air and sea, it remained in Japanese hands throughout the war.

The US Navy undertook two night evacuations of the native population, in September 1944 and March 1945, and these brought out more than 1,100 civilians.

Maloelap atoll is about 30 miles (48 km) long from north-west to south-east and 8 to 15 miles (12.9 and 24 km) wide, and was the Japanese major base closest to the Hawaiian islands group. The largest of Maloelap’s 64 islands are on the south-eastern end, where a large airfield complex had been built. This was considered by the US forces to be the most important Japanese airfield between Tarawa in the Gilbert islands group and Truk in the Caroline islands group.

The Japanese built a large naval airfield here, on the main island of Taroa: this X-shaped facility had 4,265-ft (1300-m) and 4,920-ft (1500-m) runways and so many buildings that raiding US pilots likened it to Ford Island in the middle of Pearl Harbor. The Japanese also developed some port facilities. These were protected by two anti-aircraft batteries. When the Pacific War broke out, some 21 H6K 'Mavis' flying boats of the Yokohama Kokutai were based at Taroa, along with 12 Mitsubishi A5M 'Claude' single-engined fighters of the Chitose Kokutai. The atoll was garrisoned by the 52nd Guard Force.

The airfield at Taroa was not discovered by the US forces until the carrier raids of 1 February 1942, when naval aircraft under the command of Vice Admiral William F. Halsey heavily damaged the airfield, sank one transport vessel and one submarine chaser, damaged six other ships, and killed the naval air station’s commander, Vice Admiral Sukeyoko Yatsushiro.

Mili atoll is about 20 miles (32 km) long from west-north-west to south-east and about 10 miles (16 km) wide. The atoll’s 30 islands are distributed around most of the atoll’s rim, which encloses a large anchorage with an area of 293 sq miles (759 km˛) and an open eastern side. By September 1943 the Japanese had completed an airfield with two 4,265-ft (1200-m) in an X shape with the two one side of the intersection connected by a third runway. This was the only Japanese airfield within fighter range of the Ellice islands group, and fighters from Mili escorted some of the Japanese attacks against the Ellice islands group as the US forces undertook their 'Galvanic' operations to take Tarawa and Makin islands.

The atoll was bypassed by the Allies after their capture of Kwajalein in February 1944. Thereafter only a very limited flow of supplies reached the island, by submarine, but at the cost of I-32 and I-184. By the time of the surrender in August 1945, the 4,700 men stranded on the atoll had suffered 1,600 deaths from disease, starvation or food poisoning, and another 900 had been killed or died of wounds received in air raids.

All these island bases were subordinate to the 6th Base Force on Kwajalein, formed in December 1941 and itself under the command of the 4th Fleet at Truk, and at the more local level their defence was the responsibility of the 6th Defence Force. In October and November 1941, the 51st, 52nd and 53rd Guard Forces had been despatched to defend Jaluit, Maloelap and Wotje respectively, and during the summer of 1943 these units were redesignated as the 62nd, 63rd and 64th Guard Forces respectively, and the new 66th Guard Force was assigned to Mili during June. Mili was intended for service as an aircraft staging base for offensive operations, never implemented, into the Ellice, Fijian and Samoan island groups. Imperial Japanese army units began to arrived in the Marshall islands group late in 1943 as the Japanese established their new National Defence Zone. Among these army units was the 3/107th Regiment of Lieutenant General Shunsaburo Mugikura’s 52nd Division, and this was assigned to Mili. The senior Japanese naval commander in the bypassed Marshall islands group was Rear Admiral Nisuke Masuda, who had his headquarters on Jaluit.

Before they started to implement their 'Flintlock' operation at the end of January 1944, the US forces appreciated that it was essential that the airfields on these atolls be completely neutralised to ensure the comparative security of the invasion fleet. These bases had previously been subjected to air attacks during the course of the 'Galvanic' operation against Gilbert islands group, but beginning in November 1943 they were struck by repeated heavy attacks by US Navy carrierborne and US Army Air Force land-based bombers launched from the Ellice islands group and Canton island. The first post-'Galvanic' attacks were flown against Mili, Jaluit and Maloelap on 18, 23 and 26 November respectively. Jaluit, from which the Japanese had withdrawn most aircraft by this time, was effectively neutralised by the first attack, but continued to be subjected to more raids. Mili had bee effectively neutralised by 2 December, but stubborn Maloelap did not succumb until 2 January 1944. Attacks on Wotje did not start until 13 December, and by 26 December the island had been neutralised. Raids continued on all of these atolls throughout the Marshall islands campaign the further to soften the Japanese defence forces, which on the four islands totalled 13,700 Imperial Japanese navy personnel, Imperial Japanese army troops and civilian employees: 2,200 on Jaluit, 3,100 on Maloelap, 3,300 on Wotje and 5,100 on Mili.

After the US capture of the primary target areas in the Marshall islands group, these four islands were bypassed and effectively placed under a state of siege by the 4th Marine Base Defence Air Wing on Kwajalein with its aircraft groups operating from Engebi island in Eniwetok atoll, Roi island in Kwajalein and Majuro atoll. US Navy and US Army aircraft also participated in the steady reduction of the bypassed atolls of the Marshall island group. Attacks after the end of 'Flintlock' began in March 1944 and lasted until the end of the Pacific War. Including the attacks before the start of 'Flintlock' and the attacks during the campaign, the air arms of the three US armed services dropped almost 13,000 tons of bombs on Japanese installations on these four atolls. While the Japanese arguably became some of the most practised anti-aircraft gunners in the Pacific theatre, for the US air crews it was a monotonous campaign of daily 'milk runs' in a seemingly unending effort to destroy the garrisons, although in the process they did arguably receive valuable bombing practice before moving on to more offensive operations.

Japanese attempts to sustain themselves by the growing of crops were countered by fire bombings and aerial spraying with Diesel fuel. Of the 13,700 Japanese on the atolls, therefore, by the end of the war 2,564 had been killed in action and 4,876 had died of disease and/or starvation. On all but Jaluit, where Masuda managed to maintain morale and prevent starvation, the defenders of the other islands had become totally demoralised by the war’s end. On 2 September 1945, Vice Admiral Chuichi Hara, commander of the 4th Fleet, and Mugikura, now commander of the 31st Army as well as the 52nd Division, surrendered on Truk. This surrender applied to the forces on the bypassed atolls of the Marshall islands group, where Masuda committed suicide on Jaluit rather than face questioning about the fates of airmen who had been shot down over the islands.