'Catchpole' was the US seizure of Eniwetok atoll in the Marshall islands group (17/23 February 1944).

Codenamed 'Downside' during the 'Catchpole' landing, the Eniwetok atoll was later codenamed 'Babacoote' and finally 'Begrudge', and lies 540 miles (870 km) to the north-west of Jaluit and 337 miles (542 km) to the north-west of Kwajalein, and as such is the most north-westerly atoll of the western Ralik chain of the Marshall islands group. Itself the most westerly of the island group, Ujelang is its nearest neighbour, some 130 miles (210 km) to the south-east.

In 1944 the atoll was home to fewer than 100 native inhabitants.

Eniwetok is an approximately oval atoll with some 40 islands and islets possessing a total land area of slightly less than 2.26 sq miles (5.85 km²), and is 21 miles (34 km) long on its north-west/south-east axis and 17 miles (27.5 km) across its centre. Some 5 miles (8 km) wide, the Wide Passage on the atoll’s southern side is the main passage into the lagoon, which has an area of 388 sq miles (1005 km²), and in World War II terms provided a good anchorage for as many as 2,000 ships.

Codenamed 'Privilege' and the island for which the atoll in named, Eniwetok is the largest in the atoll and lies on the eastern side of Wide Passage. From Eniwetok the atoll is an almost unbroken oval reef line right round its 64-mile (103-km) perimeter to an islet on the western side of Wide Passage. Parry island, codenamed 'Heartstrings' and later 'Overbuild', is the third largest land mass of the atoll, and lies 2.25 miles (3.6 km) to the north-east of Eniwetok island and, at its northern end, is the Deep Passage, 1 mile (1.6 km) wide, into the lagoon. On the northern side of the Deep Passage is Japtan island ('Ladyslipper'). About 1.5 miles (2.4 km) inside the lagoon and inside the central point of the Deep Passage is Jeroru islet ('Lilac'). Following the curve of the reef round to the atoll’s north side is a string of scattered islets terminating at Engebi island ('Fragile', later 'Outgeneral'), the atoll’s second largest land mass. Another line of islets extends thence to the south-east. The West Spit, which is the most westerly part of the atoll’s reef, has no islands, and there is a pair of islets, together constituting Rigili ('Posy'), about one-third of the way between the West Spit and the western side of the Wide Entrance. About 5 miles (8 km) to the south-east of Rigili is a narrow unnamed passage, and to the south-east of this a short string of islets extends to the western side of the Wide Entrance.

Of the atoll’s fringing coral reefs, that on the ocean side is farther offshore, while on the lagoon side the reefs is closer inshore with gaps.

The Japanese created a minor defensive capability on the three largest islands, and it was these which were assaulted by a joint US Marine Corps and US Army force in 'Catchpole'. Each of these islands had one or two short piers and boat landings.

The Germans had established their colony of the Marshall islands group in 1885, and together with the rest of this islands group Eniwetok was taken by forces of the Imperial Japanese navy in 1914 during the first part of World War I. The group was mandated to Japan by the League of Nations in 1920, the Japanese then administering the island under the terms of their South Pacific Mandate but in general leaving local matters in hands of the islands' traditional leaders until the start of World War II. Before the outbreak of the Pacific War, the Japanese established no military facilities in Eniwetok atoll, and it was only in December 1942 that they started work on the construction of an airfield on Engebi island after a force of 800 labourers had reached the island during the preceding month. This airfield was completed in the middle of 1943 with two runways including one 4,025 ft (3680 m) long and capable of coping with bombers. In January 1943, a small detachment of the 61^st Guard Force had arrived from Kwajalein to establish observation positions on Engebi and Eniwetok islands. This initial detachment was replaced in October of the same year by a 60-man detachment, which emplaced two 4.7-in (120-mm) coast-defence guns on Engebi. The airfield was not used until November, when it became a way station for aircraft being pulled back from Japanese outer defence line in the central Pacific to the west and bases in the Caroline islands group.

As it became evident to the Japanese that US forces might soon advance to the Marshall islands group, radar equipment was added to the establishments on Eniwetok and Parry islands, three heavy and 28 light anti-aircraft guns reached the atoll a matter of days before the start of 'Catchpole', and a combat unit had also been deployed to the atoll. This last was a new army unit, Major General Yoshima Nishida’s 1^st Amphibious Brigade, which had been created in Manchukuo from a railway security unit. This had been despatched to Truk atoll in the Caroline islands group, where some of its 4,000 men were detached for service on Maloelap, Kwajalein and Wotje, but the other 2,600 men of this self-contained unit reached Eniwetok on 4 January 1944, just six weeks before the start of 'Catchpole'.

The island was wholly devoid of realistic defences, and work on the establishment of these was immediately started by construction troops, labourers, air unit service personnel, and marooned sailors and airmen. The 3,500 Japanese at Eniwetok possessed greater combat effectiveness than those at Kwajalein, but the latter’s longer-established defences were considerably better. The headquarters of the 1^st Amphibious Brigade and most of the combat troops were deployed on Parry, to a total of 1,350 troops and labourers, on Engebi were located almost 1,300 troops and labourers, but with a higher percentage of support personnel to combat troops than on Parry, and slightly more than 800 troops held Eniwetok.

There was the opportunity to create only hasty defences on each of the islands, but some of the most effective were those on Eniwetok. Since these defensive positions were of simple concept and construction, however, few of them were detected by US aerial reconnaissance.

Of basically triangular shape, Engebi is low and essentially flat, measuring 1,500 yards (1370 m) on its concave north-western side, 2,000 yards (1830 m) on its eastern side and 2,100 yards (1920 m) on its south-west side. A 3,950-ft (1200-m) runway was aligned parallel with the north-western shore, and this constituted the atoll’s only airfield. To obtain this length, the airfield’s south-eastern end, near Weasel Point on the north-western corner, had been extended slightly into the lagoon by the dumping of coral: this was an effort which was not common in Japanese construction thinking. The majority of the various support facilities was established along the south-western shore, which featured a paved road from the airfield to Skunk Point on the island’s south-eastern corner. From there, a road extended along the eastern shore to Newt Point on the island’s north-eastern corner. There was a short pier toward the centre of the south-western shore.

Most of the island was only lightly vegetated with brush and scattered palms, but the east central portion was more thickly covered by palms and underbrush, and the north-eastern corner by very dense brush.

The surrounding coral reef was both flat and wide, and was without natural obstacles on the south-western, or lagoon, side.

Eniwetok island is 2 miles (3.2 km) long on its north-east/south-west axis, and 450 yards (410 m) wide near its south-western end. Eniwetok is unique among the atoll’s islands in that the lagoon side is faced by a steep bluff, between 8 and 15 ft (2.4 and 4.6 m) high, immediately behind the narrow beach. This was to prove a difficult obstacle to overcome. An earth road extended along almost three-quarters of the island’s length from its south-western end. On the south-eastern shore, facing the ocean, the coral reef extended between 100 and 200 yards (90 and 185 m) offshore, and off the south-western end between 70 and 150 yards (65 and 140 m). Along the southern portion of the north-west coast, facing the lagoon, the coral reef extended between 200 and 500 yards (185 and 460 m) offshore, but presented no major obstacle, and there were also inshore fringing reefs. Along about three-quarters of the rest of the island’s north-western shore there were broken fringing reefs and coral outcroppings.

Only limited support facilities had been constructed on Eniwetok.

Parry island has a teardrop shape, and is 2 miles (3.2 km) long and just under 600 yards (550 m) wide near its northern end, Neck Point. The southern end, which tapers to a point, was named Slumber Point. The island is low and flat, and for the most part was covered by a dense growth of palms and brush except on the upper portion of the western side, which was relatively clear. On the eastern side facing the ocean and the northern end, the coral reef is between 200 and 300 yards (185 and 275 m) wide. On the lagoon side the reef fringes the shore along most of the island’s length, but along the upper central portion it is free of reefs, although there are a few coral outcrops between 300 and 500 yards (275 and 460 m) off this area as well as off the lower part of the western shore. An earth road encircled the island close to the shore, and a small seaplane base and a radio-direction finding station were located on the upper central portion of the western shore. There were two piers, of which the longer, southern, unit was known as Valentine Pier.

'Catchpole' was the final major element of the US seizure of the Marshall islands group using the forces which had been earmarked for the cancelled assault on Kavieng in New Britain and then allocated as the reserve for the capture of Kwajalein in 'Flintlock', and the operation’s success provided the US forces with an airfield and harbour for the support of attacks on the Mariana islands group to the north-west. As it had not been necessary to commit the floating reserve during the 'Porcelain' assault on Kwajalein, and as a result of erroneous intelligence suggesting that Eniwetok was only lightly garrisoned, Admiral Chester W. Nimitz, commander-in-chief of the Pacific Fleet and Pacific Ocean Areas, authorised his commanders to advance the timetable for landings on Eniwetok, originally scheduled for 1 May, using nine transport vessels with the 8,000 men of the 106^th Infantry and 22^nd Marines (the Eniwetok Expeditionary Group, or Task Group 51.11) under the command of Brigadier General Thomas E. Watson.

Scheduled for 15 February, the operation was then postponed by two days to allow Japanese air and naval strength at Truk to be neutralised in 'Hailstone' by the aircraft of TF58. The aircraft raided Truk on 17/18 February, discovering no major Japanese warships but destroying about 275 aircraft and sinking some smaller combatants (two light cruisers, three auxiliary cruisers, four destroyers, two submarine tenders, one armed trawler, and one aircraft ferry) together with 24 merchant ships totalling some 200,000 tons, all for the loss of just 25 US carrierborne aircraft.

TG51.11 had initially been deployed from the Hawaiian islands group to Kwajalein, where it arrived on 3 February for its landing force, 1^st Tactical Group, to serve as the floating reserve for 'Flintlock'. The 1^st Tactical Group was a joint provisional force formed by the V Amphibious Corps and built around the separate 22^nd Marines and 106^th Infantry (less its second battalion) detached from Major General Ralph C. Smith’s 27^th Division. In its primary form as the Eniwetok Expeditionary Group departed Kwajalein atoll on 15 February. Attacks on Eniwetok by carrierborne warplanes had started on 30 January, when all of the Japanese aircraft on Engebi were destroyed, and continued up to the landing.

Vice Admiral (from 21 February Admiral) Raymond A. Spruance’s 5^th Fleet (including the fast carrier task groups of Vice Admiral Marc A. Mitscher’s Task Force 58) was responsible for the complete campaign, with Rear Admiral Richmond K. Turner’s 5^th Amphibious Force entrusted with the assault operation using Rear Admiral Harry W. Hill’s Task Group 51.11 (Eniwetok Expeditionary Group). Land-based air support was furnished by Major General Willis H. Hale’s US 7^th AAF operating from bases on the Ellice islands group. The amphibious forces assigned to the campaign were the US Marine Corps and US Army formations of Major General Holland M. Smith’s V Amphibious Corps.

TF51.11 comprised two troop-carrying destroyer conversions, eight attack transports, one attack cargo ship, one dock landing ship, nine tank landing ships and six infantry landing craft for the task of transporting and landing the 8,000 men.

Escort for the assault force was provided by the destroyers Aylwin, Dale, Dewey, Farragut, Franks, Haggard, Hailey, Hazelwood, Heermann, Hoel, Hull, Johnston, McCord, Monaghan and Trathen.

Major gunfire support was provided by Rear Admiral Jesse C. Oldendorf’s Fire Support Group comprising the battleships Colorado, Pennsylvania and Tennessee, and the heavy cruisers Indianapolis, Louisville and Portland. Close air support was the responsibility of Rear Admiral Van H. Ragsdale’s Air Support Group comprising the escort carriers Chenango, Sangamon and Suwanee escorted by the destroyers Ellet, Hughes, Morris and Mustin.

The landing had longer-range cover and support in the form of Rear Admiral Samuel P. Ginder’s TG58.4, comprising the fleet carrier Saratoga, the light fleet carriers Princeton and Langley, the heavy cruisers Baltimore and Boston, the light cruiser San Juan, and the destroyers Case, Craven, Cummings, Dunlap, Fanning, Gridley and Maury.

The Eniwetok Expeditionary Group arrived off the south-eastern passages to Eniwetok’s lagoon early in the morning of 17 February, and the bombardment of Japtan, Engebi, Eniwetok and Parry began immediately. After the passages had been swept for mines, the transports carrying the landing force entered the lagoon through the Wide Passage and the warships of the bombardment force through the Deep Passage. By 14.00 the Reconnaissance Company of the V Amphibious Corps had secured unoccupied Aitsu ('Camellia') islet and Rujioru ('Canna') islet to the south-east of Engebi to block the way for any attempt by the Japanese to escape from Engebi, and at 03.27 on 18 February marine scouts secured Bogon ('Zinnia') islet to the north-west of Engebi. Artillery battalions were emplaced on the first two, thereby completing the operation’s first phase. The two artillery battalions were to support the assault on Engebi, which was thought to be the most strongly defended of the three island targets.

It is worth noting that there had been considerable confusion in the course of these first landings as the convoy guide, the submarine chaser SC-1066, had taken position off the wrong island. Her commander was summarily relieved, as too was the artillery commander, who had failed to get his guns and ammunition ashore as speedily as expected.

The Reconnaissance Company of the V Amphibious Corps scouted the beaches of Engebi during the night of 17/18 February.

The operation’s second phase began on the following day as the 22^nd Marines assaulted Engebi’s south-western shore across Beaches Blue 3 (2/22^nd Marines) and White 1 (1/22^nd Marines followed by the 3/22^nd Marines), the two beaches being separated by the central pier. Landing at 08.45, the leading battalions rolled up the Japanese beach positions and pushed across the island, meeting the heaviest resistance in the central palm grove and the south-eastern corner near Skunk Point. The island was prematurely declared secure at 14.50, but organised resistance was finally overcome only at 08.00 on 19 February. More than 1,200 Japanese, Okinawans and Koreans had been killed on Engebi, and the US forces had taken 16 prisoners. The US casualties had been 85 men killed and missing, and 521 men wounded.

While the initial landings were being made, the US fast carriers sent their warplanes to savage the Japanese bases at Truk atoll in the Caroline islands group and Saipan in the Mariana islands group to prevent these from being used to launch air attacks on the US forces at Eniwetok.

Documents captured on Engebi had meanwhile revealed that there were considerably larger numbers of men on Eniwetok and Parry than the Americans had believed: the totals were indicated as 808 men on Eniwetok and 1,347 on Parry. The invasion force’s commander, Rear Admiral Harry W. Hill commanding Amphibian Group 2 of the 5^th Amphibious Force, therefore decided that prudence demanded a change from the planned simultaneous landings on Eniwetok and Parry so that the maximum possible strength could be brought to bear on the former. At the same time the ammunition allotment for the preliminary gunfire bombardment was also doubled.

The operation’s third phase started on 19 February, when the US plan called for both Eniwetok and Parry to be seized. Backed by a marine battalion, the 106^th Infantry assaulted the lagoon shore of Eniwetok, landing across Beaches Yellow 1 and Yellow 2 at 09.17. Although the Japanese resistance was little more than sniper fire, the assault force was soon tangled in front of the bluff behind the beach, which to prevented the US armour from moving inland, and also persuaded a not inconsiderable number of men to start digging in, quite contrary to orders. Watson sent a stinging rebuke to the landing force commander ordering him to get his troops off the beach, and by 10.45 the beach-head had been cleared. The Japanese resistance stiffened farther inland, and the marine reserve battalion ran into a stiff pocket of resistance almost as soon as it landed, but the US advance meant that the island was soon been cut in two. Single army and marine battalions then drove toward the south-western end, where the strongest resistance was encountered, but this had been reduced by 19.00. A Japanese counterattack had caused some confusion around 12.00, but this was defeated. At the same time one army battalion pushed up Eniwetok’s long, narrow tail to its north-eastern end. Progress on this end of the island was slow, and here the Japanese had not been defeated until 16.30 on 21 February. Although it had taken longer to secure Eniwetok island than had been planned, the US losses had amounted to only 37 men killed and 94 wounded. The Japanese had lost about 800 men killed and 23 taken prisoner.

The fact that it took longer than expected to secure Eniwetok further delayed the assault on Parry. In the meantime the army artillery battalion previously emplaced on Canna was relocated to Eniwetok to support the Parry landing, and during the evening of 20 February another artillery battalion was landed on Jatpan ('Ladyslipper') islet across the Deep Passage from Parry, allowing the Americans to take Parry under fire from both the north and the south. By this time, however, weapon shortages and ammunition problems had become a major concern, and grenades, demolition charges, artillery ammunition, and even personal weapons were donated by other units to resupply and replace the losses suffered by the 22^nd Marines.

At 09.00 on 22 February, the 22^nd Marines landed on the upper portion of Parry on the lagoon side across Beaches Green 2 and Green 3 with the support of the guns of three battleships and two cruisers, and of the aircraft of three escort carriers. By 13.30 the marines had reached the island’s northern end, and the area of the seaplane base and the rest of the island had been cleared to a point about mid-way down its length. An attack by three Japanese tanks came too late to stand any chance of success as US armour, superior in number and quality, had already been landed and easily shattered the lighter Japanese tanks. The US advance was halted for the night in a position some 450 yards (410 m) from the island’s south end. That last area had been cleared by 09.00 on 23 February and the island was declared secure 30 minutes later.

The Japanese had lost about 1,300 men killed and 25 taken prisoner, while the losses of the US forces had been about 170 men killed and 230 wounded.

After this, the 106^th Infantry reverted to its parent division and remained as part of the garrison force, together with the 10^th Marine Defense Battalion that arrived on 24 February, until it was returned to the Hawaiian islands group in April. By 1 April 1944 there were some 11,200 US personnel in the various installations of Eniwetok atoll.

The 22^nd Marines moved to Kwajalein atoll for area island security, and then undertook 29 largely unopposed landings to clear the many atolls, islands and islets of the lesser Marshalls group in 'Flintlock Junior' and in the process securing the mostly unoccupied Wotho, Ujae, Lae, Namu, Ailinglapalap, Namorik, Ebon, Bikini, Rongelap, Utirik, Airluk, and Likiep atolls, and Kili and Mejit islands between 7 March and 5 April.

The development of Eniwetok as a US base soon began, the first stage being restoration of the Japanese airfield on Engebi. A new fighter airfield, with a 3,950-ft (1205-m) runway, was begun on Eniwetok and later became operational as Wrigley Field. On the southern portion of the island a new bomber airfield, with a 6,800-ft (2075-m) runway was built to create Stickell Field. A seaplane base was built on Parry island on the basis of the Japanese facilities. Limited naval base facilities were established on Eniwetok The US air base closest to the Mariana islands group, Eniwetok quickly became a major staging base for attacks on those islands, and it was at Eniwetok that the US task forces assembled for the 'Forager' campaign against the Marianas group in the summer of 1944. The advanced fleet base also supported the service elements of the British Pacific Fleet’s fleet train operating in the Pacific in 1945.

The capture of Eniwetok atoll in this small but significant campaign severed the Japanese air bridge to the Marshall islands group, and opened the way for the US advance to the Mariana islands group. The Japanese garrisons on the other atolls of the Marshall islands group (Wotje, Maloelap, Mille and Jaluit) were isolated and left to 'wither on the vine', their garrisons finally surrendering on 2 September 1945.

The loss of Eniwetok also ended any Japanese hope of being able to reinforce its garrisons on Wake island or the bypassed atolls of the Marshall islands group. The atoll’s capture also gave the US Navy a superb forward base for further advances to the north-west, and provided US warplanes with the platform which allowed them to bomb targets in the Caroline islands group.

An afterthought to the main part of 'Catchpole' was the seizure of Ujelang atoll, in the Ralik chain of the Marshall islands group. This is the most westerly island in the Marshall group, and located approximately 135 miles (217 km) to the south-south-west of Eniwetok. The island was occupied without opposition by Company I, 111^th Infantry, on 22 April 1944 and was then used as a staging area before the regiment’s redeployment to Peleliu on 1 February 1945.