Battle of Kwajalein

Battle of Kwajalein
Part of World War II, Pacific War
US marines attack a Japanese blockhouse on Kwajalein
Date January 31, 1944 – February 3, 1944 Location Kwajalein Atoll, Marshall Islands Result American victory
Belligerents
United States	Japan
Commanders and leaders
Richmond K. Turner, Holland M. Smith	Monzo Akiyama
Strength
2 divisions (about 42,000 soldiers)	About 8,100
Casualties and losses
372 killed, 1,592 wounded	7,870 Japanese dead, 105 captured, 125 Korean laborers captured

The Battle of Kwajalein was a battle of the Pacific campaign of World War II, fought from January 31, 1944 to February 3, 1944 on Kwajalein Atoll in the Marshall Islands. Employing the hard-learned lessons of the battle of Tarawa, the United States launched a successful twin assault on the main islands of Kwajalein in the south and Roi-Namur in the north. The Japanse defenders put up a stiff resistance though outnumbered and under-prepared. The determined defense of Roi-Namur left only 51 survivors of an original garrison of 3,500.

For the United States, the battle represented both the next step in its island-hopping march to Japan and a significant moral victory in that it was the first time the United States penetrated the "outer ring" of the Japanese Pacific sphere. For the Japanese, the battle represented the failure of the beach-line defense. In the future, Japanese defenses would be prepared in depth, and the battles of Peleliu, Guam, and the Marianas would prove far more costly to the United States.

The Atoll

Kwajalein Atoll is in the heart of the Marshall Islands. It lies in the Ralik Chain, 2,100 nautical miles (3900 km) southwest of Honolulu, Hawaii at 8°43′N 167°44′E. Kwajalein is the world's largest coral atoll as measured by area of enclosed water. Comprising 97 islets, it has a land area of 6.33 km², and surrounds one of the largest lagoons in the world, measuring 839.30 km² in size.

The two most significant land masses are Kwajalein Island in the south, and the linked islands of Roi-Namur in the north.

Background

By the time Japan entered World War II, The Marshalls (South Pacific Mandate), were already an integral part of the Japanese perimeter of defense. Its facilities were being utilized as outlying bases for submarines and surface warships, as well as for air staging for future advances being planned against Ellice, the Fiji Islands, and Samoa.

After the capture of Makin and Tarawa in the Gilbert Islands, the next step in the United States Navy's campaign in the central Pacific was the Marshall Island chain. These islands had been German colonies until World War I, when they were assigned to Japan in the post-war settlement as the "Eastern Mandates". The islands had become a mystery since the Japanese closed them to the outside world. It was presumed the Japanese had built illegal fortifications throughout the islands, however the precise extent of any such fortifications was unknown. To the Japanese, regarding them as part of the "outer ring" of Japanese territory held prior to 1941, this assault would be the first on what the Japanese regarded as Japanese soil.

The strategic importance of the Marshalls had been identified as early as 1921 in the famous Plan Orange — the American interwar plan for a possible conflict with Japan. The Marshalls were a key step in the island-hopping march to Japan itself.

After the loss of the Solomon Islands and New Guinea in 1943, the Japanese command decided that the Gilbert and Marshall Islands would be expendable. They preferred to fight a decisive battle closer to home. However, at the end of 1943, the Marshalls were reinforced to make their taking expensive for the Americans. By January 1944 the regional commander in Truk, Admiral Masashi Kobayashi, had 28,000 troops to defend the Marshalls, but he had very few planes.

Japanese Planning and Preparations

Actual defenses on the Marshalls, however, were never very substantial or heavily manned. After nearly 10 years of construction, fortifications on the Marshalls were considerably inferior when compared with Tarawa, which had been turned into a fortress in less than eighteen months.

In addition, less than half of the troops stationed in the Marshalls were combat trained, the rest being support and labour troops with little or no combat training. It was not until after the Japanese position in the Solomons and New Guinea began to deteriorate that Imperial Headquarters made plans to strengthen the Marshalls. In fact, by September 1943, the Japanese High Command had written off the Gilberts and Marshalls as lost, deciding that the areas should be to used to fight a delaying action while a new defense perimeter was created from the Banta Sea through the Carolines and the Marianas. Additionally, combat units were ordered to the Marshalls from the Philippines, Manchukuo, and the homeland, with additional air power to be flown in from both the homeland and nearby Truk.

The 6th Base Force, under command of Rear Admiral Monzo Akiyama, and headquartered on Kwajalein, was the principal defense force of the islands. Akiyama, however, had his men spread out over a very wide area, mostly concentrating on the defense of those atolls (Jaluit, Mille, Maloeap, and Wojte) that were never considered vulnerable to American attack. Those reinforcement troops 2nd Battalion/1st Amphibious Brigade under Colonel Aso (9 Type 94/97 Tankettes 2 companies of Type 2 Ka-Mi Amphibious Tank (as SNLF Kwajalein Tank Detachment) finally arrived and were quickly dispersed by Akiyama, mainly to the outlying atolls.

Kwajalein was to remain undermanned, underequipped, and unprepared for the assaults being arrayed against it. Overall Japanese strength on these islands numbered approximately 8,000 men, of which less than half were considered combat effective. On Kwajalein proper, the troops were made up mostly of labour forces, a good number of those being Koreans. On Roi-Namur, the troops were mostly JNAF land personnel who had little ground combat training and who were underequipped for such a function.

The defense system on the islands was mostly in line, with little or no depth. Although some fortified areas existed, none were as extensive or well armed as those of Tarawa. In addition, there were several defenses that mostly concentrated on any assault coming from the ocean side; no coastal defense artillery had been placed on key islets guarding passages to the lagoon, and there was little or no use of mines. Despite shortfalls, efforts to strengthen ground defenses continued. Still, Akiyama's greatest defense remained his aerial offensive capability. He had well manned air bases on Roi-Namur, Maloeap, Wojte, Mile and Eniwetok, detached Chitose and 653th Air Corps Mitsubishi A6M fighters with the nearly complete Mitsubishi G3M and G4M bomber base in Kwajalein. In addition, he had some Nakajima A6M2-N and Mitsubishi F1M detached in seaplane bases on Burton, Jaluit, Wojte, Majuro, Taongi, and Utirik.

During the month of November, however, both USAAF land-based and US Navy carrier-based bomber attacks, in conjunction with the American assault on the Gilberts, had destroyed 71 of Akiyama's fighters and bombers. Reinforcements flown in from the homeland and Truk replenished most of his losses, but he could expect little additional help in the future. The Japanese war industry was falling far short of needed production, affecting all branches of the armed services, including the Japanese Carrier Air Arm, which had long since retreated from the Central Pacific. In fact, the 32 planes flown from Truk were the last of the carrier aircraft left behind following that retreat. Akiyama was therefore not expected to defeat his adversary, but rather to delay the Allied forces advance while exacting the greatest possible toll upon them.

U.S. Planning and Preparation

Expecting the U.S. to attack the outermost islands in the group first, most of the defenders were stationed on Wotje, Mille, Maloelap, and Jaluit to the east and south. Indeed, the original American plan called for a cautious series of steppingstone attacks starting in the eastern Marshalls. The Japanese troop dispositions were revealed to the Americans by ULTRA decryptions of Japanese communications, and Admiral Chester Nimitz decided instead to bypass these outposts and attack the Kwajalein Atoll directly, knifing into the very heart of the Marshall Islands. The operation was given the code name Operation Flintlock.

There were two main objectives: The linked islands of Roi-Namur in the north, and Kwajalein Island at the south end of the atoll. The 4th Marine Division under Major General Harry Schmidt was assigned to Roi-Namur, and the Army's 7th Infantry Division under Major General Charles H. Corlett would make the assault on Kwajalein.

To ensure the success of the operation, sea and air superiority were necessary. Accordingly, on January 29, 1944, US carrier planes attacked the Japanese airfield on Roi-Namur, destroying 92 of the 110 Japanese planes in the Marshalls.

Staging through Baker Island airfield Rear Admiral J.H.Hoover's Consolidated B-24 "Liberators" of the Seventh Air Force, quickly set their sights upon their targets. In the beginning, the most important were Mille, the Japanese base closest to the Gilberts and Maloeap, the most powerful enemy bases threatening the upcoming operations. Mille was the subject of several attacks through the month of November, causing considerable damage to installations and high losses of aircraft for the Japanese. But Mille remained the only base within fighter reach of the Gilberts and the defenders managed to keep the facilities there operational and reinforced with aircraft. Following the capture of Tarawa, and through December 19, 106 B-24s dropped a total of 122 tons of explosives on Mille's airbase. The largest of those raids came on December 4 when 34 B-24s pulverized the atoll in conjunction with carrier-based bombing raids of other parts of the Marshalls. On December 18 Hoover initiated renewed strikes against enemy targets on Mille with land-based A-24 Dauntless dive bombers and Bell P-39 Airacobra making their debut in the Marshall air offensive. Japanese losses for the day amounted to 10 fighters (four on the ground) and four damaged. Other aircraft types participating in the offensive included B-25 Mitchell and Curtiss P-40 Warhawk.

In addition it was necessary to take another atoll in the eastern Marshalls — Majuro. Majuro is 220 miles southeast of Kwajalein and could serve as an advanced air and naval base as well as safeguard supply lines to Kwajalein. Majuro was very lightly defended and only the V Amphibious Corps Marine Reconnaissance Company and the 2d Battalion, 106th Infantry, 7th Infantry Division were employed in the capture of Majuro. The Island was taken on January 31, without any U.S. casualties.

The Assault

The U.S. forces for the landings were Rear Admiral Richmond K. Turner's 5th Amphibious Force, and Major General Holland M. Smith's V Amphibious Corps, which comprised the 4th Marine Division commanded by Maj. Gen. Harry Schmidt, the 7th Infantry Division commanded by Maj. Gen. Charles H. Corlett, plus the 22nd Marine, 106th Infantry, and the 111th Infantry regiments. The 4th and 7th Divisions were assigned to the initial landings at Kwajalein, while the 2nd Battalion of the 106th was assigned to the simultaneous capture of Majuro Atoll, about 490 km to the southeast. The rest of the 106th and the 22nd Marines were in reserve for Kwajalein, while awaiting the following assault on Eniwetok, scheduled for three months later.

The 7th Infantry Division began by capturing the small islands labeled Carlos, Carter, Cecil, and Carlson on January 31, which were used as artillery bases for the next day's assault. Kwajalein Island is 4 km long but only 800 m wide. There was therefore no possibility of defence in depth and the Japanese planned to counter-attack the landing beaches. They had not realized until the battle of Tarawa that American amphibious vehicles could cross coral reefs and so land on the lagoon side of an atoll; accordingly the strongest defences on Kwajalein faced the ocean. The bombardment by battleships, B-29 bombers and artillery on Carlson was devastating. The US Army history of the battle quotes a participant as saying that "the entire island looked as if it had been picked up 20,000 feet and then dropped." By the time the 7th Division landed on Kwajalein Island on February 1, 1944, there was little resistance; by night the Americans estimated that only 1,500 of the original 5,000 defenders were still alive.

On the north side of the atoll, the 4th Marine Division followed the same plan, first capturing islets Ivan, Jacob, Albert, Allen, and Abraham on January 31, and landing on Roi-Namur on February 1. The airfield on Roi (the eastern half) was captured quickly, and Namur (the western half) fell the next day. The worst setback came when a Marine demolition team threw a satchel charge of high explosives into a Japanese bunker which turned out to be a torpedo warhead magazine. The resulting explosion killed twenty Marines and wounded dozens more. Only 51 of the original 3,500 Japanese defenders of Roi-Namur survived to be captured.

The Aftermath: Lessons Learned

The relatively easy capture of Kwajalein demonstrated US amphibious capabilities and showed that the changes to training and tactics after the bloody battle of Tarawa had been effective. It allowed Nimitz to speed up operations in the Marshalls and invade Eniwetok Atoll on February 17, 1944.

The Japanese learned from the battle that beachline defenses were too vulnerable to bombardment by ships and planes. In the campaign for the Mariana Islands, the defense in depth on Guam and Peleliu was much harder to overcome than the thin line on Kwajalein.

References

Books

• Bailey, Dan E. (1992). World War II: Wrecks of the Kwajalein and Truk Lagoons. North Valley Diver Publications. ISBN 0-911615-05-9.
• Marshall, S. L. A. (2001). Island Victory: The Battle of Kwajalein Atoll. University of Nebraska Press. ISBN 0-8032-8272-9. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Morison, Samuel Eliot (1961). Aleutians, Gilberts and Marshalls, June 1942-April 1944, History of United States Naval Operations in World War II. Boston: Little, Brown and Company. ASIN B0007FBB8I. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
• Rottman, Gordon (2004). The Marshall Islands 1944: "Operation Flintlock, the capture of Kwajalein and Eniwetok". Osprey Publishing. ISBN 1-84176-851-0. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

Web

• US Army Campaigns in World War II: Eastern Mandates
• Chapin, Captain John C., USMCR (Ret), Breaking the Outer Ring: Marine Landings in the Marshall Islands, Marines in World War II Commemorative Series, History and Museums Division, United States Marine Corps, 1994.
• Soldiers of the 184th Infantry, 7th ID in the Pacific, 1943–1945
• Animated History of The Battle for Kwajalein
• Heinl, Robert D., and John A. Crown (1954). "The Marshalls: Increasing the Tempo". USMC Historical Monograph. Historical Division, Division of Public Information, Headquarters U.S. Marine Corps. Retrieved 2006-12-04.{{cite web}}: CS1 maint: multiple names: authors list (link)