This was the US seizure of the island of Kwajalein in the Kwajalein atoll of the Marshall islands group in the central Pacific Ocean (31 January/8 February 1944).
Kwajalein atoll lies near the geographical centre of the Marshall islands group in the central part of the Pacific Ocean, and in the central portion of the western Ralik chain. Namu atoll, its nearest neighbour, is some 40 miles (65 km) to the south-east, and Kwajalein is 337 miles (542 km) to the south-east of Eniwetok atoll and 245 miles (395 km) to the north-east of Jaluit atoll. Truk atoll in the Caroline islands group is 925 miles (1490 km) to the west, and Guam in the Mariana islands group is 1,320 miles (2125 km) to the west-north-west.
Kwajalein is the largest atoll in the world, and has a length of 66 miles (106 km) and width of 20 miles (32 km), and its lagoon has an area of 839 sq miles (2174 km˛), which was sufficient to accommodate the whole of the US Pacific Fleet in World War II. The atoll comprises 97 islands and islets, of which 38 are of significant size, but possesses only 6.33 sq miles (16.4 km˛) of land, and the average height of the land above sea level is a mere 6 ft (1.8 m).
In overall configuration, the atoll is a misshaped triangle with numerous breaks in the reef providing access into the lagoon. The atoll is basically two arms, the south and the west with a small portion extending to the north, areas which are normally known as western, southern, and northern or north-eastern Kwajalein. While islands and islets are scattered on most of the reef’s length, there is a gap constituting the Tabik Channel, 15 miles (24 km) wide and with only its western part passable at low tide because of a submarine reef on the southern side of the western arm. The larger islands are concentrated in four areas: two of these were bypassed by the war, namely the western end of the western arm with Ebadon island and a number of islets, and the eastern portion of the western arm’s southern side, an area to the east of the Tabik Channel and where the southern arm turns to the south with Ennugenliggelap, Yebbenohr and Nell islands as the most notable.
On the end of the southern arm is the atoll’s largest island, Kwajalein, while on the northern lode are the twin islands of Roi and Namur. To the north of Kwajalein is the considerably smaller Ebeye island, which was also defended by the Japanese. These were the main objectives for 'Flintlock'. Both these areas possessed numbers of smaller islands, some of which were used by the US forces as artillery firing positions to support the assault on the main islands.
Even though these island objectives were in the same atoll and part of the same operation, they were fought as independent battles as the islands of Kwajalein ('Porcelain') and Roi-Namur ('Burlesque' and 'Camouflage') are 42 miles (67.5 km) apart.
The many islets in the area of Kwajalein and Roi-Namur were also codenamed and are often used as many of the local names are very similar and some have no known local names. In general, the codenames for islets in the area of Roi-Namur began with A and those in the area of Kwajalein with B and C, although there were exceptions.
Located in the extreme south of its eponymous atoll, Kwajalein is a crescent-shaped island with its convex side on the ocean or southern side, and is 2.5 miles (4 km) long with an average width of 800 yards (730 m) along most of its length but narrowing to 300 yards (275 m) at the northern end. Kwajalein and its neighbouring islands were covered with palms, pandanus trees, and salt brush, and the woods were at their densest on Kwajalein’s northern end. The western end was also wooded, but in a large clearing the Japanese had erected a radio direction-finder station known to the US forces as the Wart Area. A low anti-tank sea wall had been built along the shore, but this proved to be only a minor hindrance to the assault force. A road encircled the entire island, and several connecting roads crossed the island. The Center Pier, comprising two wharves each 100 yards (90 m) long, was sited in the centre of the northern shore, and the L-shaped Nob Pier, 500 yards (460 m) long, extended into the lagoon at a point some 800 yards (730 m) from the island’s northern end. A large number of support buildings, workshops, barracks and warehouses had been constructed along the northern shore between the Center Pier and the island’s northern end, which sported many large structures. A large headquarters building complex, known as the Admiralty Area, was sited inland at the point where the island turns distinctly north.
Most of the Japanese defences had been erected along the island’s ocean side and the northern and western ends. The airfield, with a 5,000-ft (1525-m) runway, was located in the central part of the island to the south of the Center Pier. Kwajalein was the headquarters for the 61st Base Force, under the command of Rear Admiral Monzo Akiyama, the 6th Submarine Base Force, the 6th Communications Unit, a detachment of the 4th Fleet Construction Unit, air service personnel, and the main body of the 61st Guard Force along with one company of the 4th Yokosuka Special Naval Landing Force, in ll totalling some 4,000 naval personnel. Also located on the island were more than 800 Imperial Japanese army troops of the 1st Amphibious Brigade, either assigned to support the island’s defence or on their way to Wotje atoll.
On the island’s ocean side, the reef is between 100 and 130 yards (90 and 120 m) wide, smooth and level, and wholly exposed at low tide. The surf is heavy on the eastern shore, more rolling on the southern shore, and is modest on the south-western corner. On the island’s lagoon side, the water is calm, but here the reef is between 500 and 800 yards (460 and 730 m) wide and littered with rocks and coral outcrops. Right round the island the beaches are 10 to 20 yards (9 to 18 m) wide rising only gently to higher ground. On the northern and western ends the slope of the beaches is still more gradual and extends inland 250 and 450 yards (230 and 410 m) respectively.
The US forces decided that before their main assault on Kwajalein, they would take a quartet of neighbouring small islands. Enubui (Carlson) is 3 miles (4.8 km) to the north-west of Kwajalein. The island is some 1,180 yards (1080 m) long and fewer than 300 yards (275 m) wide, and was the site of a radio station. On the island’s lagoon side, a pier 100 ft (30 m) long provided access. Some 4,300 yards (3930 m) to the north-west of Carlson is Ennylabegan island (Carlos), which is 1 mile (1.6 km) long and 300 yards (275 m) wide. Between these two islands is the so-called Carlos Pass, but not even small craft could cross above its submarine reef. About 9 miles (14.5 km) to the north-west of Kwajalein and 900 yards (825 m) beyond Carlos, are the islets of Gea (Carter) and Ninni (Cecil), which flank the Gew Channel (Cecil Pass), which at 900 yards (825 m) is a narrow but usable entrance into the lagoon, through which the attack force would enter single file. The islet of Gehh (Chauncey) to the north-west of Cecil was secured after the main landing.
To the north of Kwajalein is a string of small islands and islets which were also to be secured after the main landing. The most important of these, and the third most strongly defended in the whole atoll, was Ebeye (Burton). Located 2.5 miles (4 km) directly to the north of Kwajalein’s north-eastern tip, Ebeye is an essentially rectangular islet 1,770 yards (1620 m) long on its north/south main axis and 250 yards (230 m) wide, and posessing reefs and beaches similar to those of Kwajalein. Ebeye was spotted with palms and brush, with the densest brush and small mangroves along the ocean side. A road extended along the islet’s lagoon side, and the L-shaped Bailey Pier, built of concrete and with a secondary pier angling off its southern side, jutted 490 yards (450 m) into the lagoon from the island’s centre. Two seaplane ramps, each 100 yards (90 m) long, occupied the northern portion of the lagoon side. Many support buildings, hangars, workshops and barracks occupied much of the rest of the islet, the densest concentration of these building being in the centre. Near Bailey Pier was a radio direction-finding station.
As was the case on the atoll’s other islands, the main defences had been constructed on the ocean side, but on Ebeye additional positions had been built in the vicinity of the seaplane ramps. The islet was held by some 500 men of the guard force, communications and air service personnel.
Privy to ‘Ultra’ intelligence that the Japanese had redeployed much of their garrison to the outer atolls of the Marshall islands group in the expectation that these would be the USA’s first objectives, Admiral Chester W. Nimitz, the commander-in-chief of the Pacific Fleet and of the Pacific Ocean Areas, and Rear Admiral Forrest P. Sherman, the Pacific Fleet’s deputy chief-of-staff, were confident that Kwajalein was the right objective, and that the US forces involved could be adequately covered by Vice Admiral Marc A. Mitscher’s Fast Carrier Task Force (Task Force 58) of Vice Admiral Raymond A. Spruance’s 5th Fleet, to which overall control of ‘Flintlock’ was entrusted. The 5th Fleet’s major assault element was Rear Admiral Richmond K. Turner’s 5th Amphibious Force (including Major General Holland M. Smith’s V Amphibious Corps) with TF58 sweeping ahead of it to eliminate Japanese air strength on the Marshall islands.
Under Turner’s command, the Southern Attack Force (Task Force 52) comprised two destroyer-based transports, 12 attack troop transports, three attack transports, three dock landing ships, 16 tank landing ships and 12 infantry landing ships. Escort was provided by the destroyers John Rodgers, Hazelwood, Haggard, Franks, Schroeder and Hailey. Heavier support was provided by Rear Admiral Robert C. Giffen’s Fire Support Group with the battleships Idaho, Pennsylvania, New Mexico and Mississippi, the cruisers Minneapolis, New Orleans and San Francisco, and the destroyers McKee, Stevens, Bailey, Frazier, Hall, Meade, Colahan, Murray, Harrison, Ringgold and Sigsbee. Tactical air support was provided by Rear Admiral Ralph E. Davison’s Air Support Group (TG52.9) with the escort carriers Manila Bay, Coral Sea and Corregidor and the destroyers Bancroft, Coghlan, Caldwell and Halligan.
The Southern Attack Force arrived off the western end of Kwajalein with Major General Charles H. Corlett’s reinforced 7th Division comprising the 17th, 32nd and 53rd Infantry for the main assault, which was scheduled for 1 February.
Like the marines committed against Roi and Namur to the north, the army initially secured a number of small islands and islets, in this instance to the north-west of Kwajalein, on 31 January: these first targets included Cecil, Carter and Carlson. It was known that the Japanese had observation positions on these islands and islets, and also that an estimated 250 to 300 men defended Carlson. The task of taking these outlying parts of the Japanese defences was entrusted largely to the 17th Infantry. In the darkness just before dawn, the landing detachment of the Reconnaissance Troop of the 7th Division intended to take Cecil mistook Chauncey for Cecil and landed on it, triggering a skirmish before the mistake was discovered. Most of the US force was then withdrawn and landed on Cecil before 12.00. Chauncey was held by a force larger than had been realised, however, and the small US element had to be withdrawn. Carlos was secured quickly. The largest of the offshore islands, Carlson was assaulted at 09.12. Expecting significant resistance, the landing force found only 24 Korean labourers, who were taken prisoner. Four battalions of the divisional artillery were quickly landed to support the next day’s main assault on Kwajalein. Chauncey was finally cleared on 2 February by the 7th Reconnaissance Troop, who killed all 125 of the Japanese defenders.
The force which had taken Cecil returned to Chauncey on 2 February and killed 125 Japanese sailors from a sunken patrol boat, at a cost of three dead and 21 wounded. The troopers discovered 75 secret charts of Japanese harbours, which was a notable intelligence coup.
At 09.30 on 1 February, the 7th Division started to land on the western end of Kwajalein. Adverse weather limited the quantity of tactical air support which could be provided, but seven battleships and three heavy cruisers bombarded Kwajalein with more than 2,000 large-calibre rounds and more than 5,000 5-in (127-mm) rounds. Another 161 tons of explosives were fired by the artillery on Enubui. A landing on the concave lagoon side of the island would have been liable to being taken under a cross fire and was therefore ruled out, while a landing on the ocean side would run into the strongest defences, which included 15 pillboxes on the ocean side. The decision was therefore made that the landings would take place on the island’s extreme western end, with artillery support from Enubui and from warships on both sides of the island. The fire support proved so effective that 1,200 men of the 7th Division landed in the first 12 minutes without suffering a single casualty. The army artillery then maintained a creeping barrage ahead of the advancing US troops.
The 184th Infantry came ashore on Beach Red 1 in the western end’s northern part and the 32nd Infantry on Beach Red 2 in the southern part. Both regiments were landed by amphibian tractors on a front of about 500 yards (460 m), and immediately advanced some 950 yards (870 m) along the island, halting for the night just to the west of the Center Pier after having overrun about half of the airfield. A small counterattack at 23.00 caused a measure on initial US concern, but was then driven back. On the following day the US advance continued, with the aid of armoured support which was adequate in numbers but somewhat poorly co-ordinated, and the US troops pushed forward almost to the Admiralty Area, but the Japanese resistance increased, especially in an area of blockhouses to the south of Nob Pier, as the US infantrymen fought their way forward. The many buildings, debris from the bombing and shelling, and the large numbers of craters also resulting from the bombing and shelling all served as obstacles to the advance and also provided the defenders cover: this resulted in some of the first street fighting to take place in the Pacific War as the Americans steadily cleared the area. By the fall of night on 3 February, the 7th Division’s men had advanced almost to Nob Pier, beat off two Japanese counterattacks during the night, and reached Nero Point on the island’s northern end at 19.20 on 4 February, though the island had already been declared secure at 16.10. Mopping-up operations continued to 7 February.
The US casualties had been 58 men killed, two missing and 170 wounded. About 4,450 Japanese were killed, and 176 men, most of them Koreans, were taken prisoner.
The other islands and islets in the southern part of Kwajalein atoll were to be taken by the 17th Infantry. The most important of these, that nearest to Kwajalein and also the most strongly defended, was Ebeye. The regiment assembled on Carlos for the attack on 3 February, before which the Japanese defences had been hit by 639 tons of shells and 87 tons of bombs. As it had the weakest defences, an area 500 yards (460 m) wide was selected as Beach Orange 4: this was on the island’s lagoon side near the southern end. The regiment landed at 09.35, cut across the island’s southern end, and then turned to the north. By the fall of night half of the island, as far as Bailey Pier, had been cleared, and the attack continued on 4 February. The US infantrymen reached the island’s northern end being at 12.10, and the island was declared secure at 13.37. The 17th Infantry had lost seven men killed and 82 wounded, while it was estimated that the Japanese had lost about 450 men; seven men were taken prisoner.
Other elements of the 17th Infantry secured the small islands to the north of Ebeye between 1 and 5 February. Almost 450 Japanese were killed on these islands, and a few prisoners were also taken, at a US cost of six men killed and 11 wounded.
Thus the seizure of Kwajalein atoll operation, lasting from 31 January to 8 February, was completed. On Kwajalein island the 5,000-ft (1525-m) Japanese runway was extended to 6,300 ft (1920 m), a shorter 1,200-ft (365-m) runway was added, and support facilities were built. The airfield was initially used by the US Army, but it was transferred to the US Navy on 1 July 1945. The US Navy also established a seaplane base on Ebeye, largely by a refurbishment of the original Japanese facilities and then their expansion, and the headquarters of the Naval Operating Base and Commander, Marshalls-Gilberts, was also established there. A joint communications centre was built on Enubui, and a major ship repair station was built on northern Gugegwe (Berlin) island.