Rottman - The Marshall Islands, 1944: Operation Flintlock, the capture of Kwajalein and Eniwetok

Campaign 146

Operation Flintlock, the capture of Kwajalein and Eniwetok

Gordon L Rottman Illustrated by Howard Gerrard

Series editor Lee Johnson Consultant editor David G Chandler

Namur Island,
12 February 1944 (D+1D+2) Kwajalein Island, D+1,
1 February 1944
Eniwetok Island, 1921 February
(D+2D+4)

T he seizure of the Marshall Islands in the Central Pacific had long been recognized as a necessity in a war with Japan. As far back as 1921, Marine Major E.H. Pete Ellis had formatted a hypothetical plan to seize four Marshalls atolls to serve as staging bases for further naval operations against Japan. Ellis died under mysterious circumstances in the Japanese-controlled Palau Islands in 1923.

In May 1943 the Trident, or Washington, Conference determined the wars course and reexamined earlier decisions. In regards to the war with Japan, two thrusts would converge on the Home Islands. The main effort would be in the Central Pacific by Admiral Chester Nimitzs Pacific Fleet, with General Douglas MacArthur conducting a secondary effort in the Southwest Pacific through New Guinea and the Philippines. MacArthur argued for a concentration of effort in the Southwest Pacific, but it was felt the Japanese would mass their forces to meet one thrust. The Central Pacific route was more direct and required fewer troops. The Japanese would be unable to deploy as many troops and aircraft on the small widely scattered islands as they could in New Guinea and the Philippines. The Gilberts and Marshalls were earmarked to be seized.

US Fifth Fleet seized the Gilberts after the bloody November 1943 battles for Tarawa and Makin. Meanwhile, US and Australian forces were advancing in New Guinea. A major issue was to decide which atolls in the Marshalls would be seized. The Japanese had bases on six atolls plus Kusaie and Wake Islands. On 1 September 1943, Eniwetok Atoll (the northernmost), Kusaie Island (westernmost), and Wake Island (far to the northeast, but under control of the Japanese Marshalls forces) had been selected as targets to be taken. At this time the new 4th Marine Division (MarDiv), 7th Infantry Division (InfDiv), and the separate 22nd Marines were designated to execute Operation Flintlock (originally Bankrate) under the command of the Marine V Amphibious Corps (VAC). However, Admiral Nimitz proposed Kwajalein (the main base near the Marshalls geographic center), Maloelap, and Wotje (the latter two being closer to Pearl Harbor) as alternatives. These three atolls held 65 per cent of the air bases in the Marshalls and the other bases could be neutralized without necessarily being physically occupied. The target date was 1 January 1944. The date for the seizure of Eniwetok by 27th InfDiv was tentatively set as 1 May, however, when it became clear that the atoll was lightly defended, the assault was rescheduled for 1 March.

A pre-bombardment view of Namur Island. This is the Yokohama Pier on the islands south-central coast, the lagoon side. The pier would serve as a boundary between the two landing beaches and the two assault battalions. In the upper left corner can be seen the concrete causeway connecting Namur to Roi.

By the time of the invasion Namurs appearance had been transformed by extremely heavy naval and aerial bombardment. This view is looking south across the island into the lagoon. While devastating the islands facilities, the bombardment created obstacles to movement because of the downed trees, wreckage, and craters. It also provided hiding places for the defenders. The torpedo warehouses crater can be seen below the V of the three large concrete structures near the left edge.

Initial planning was conducted prior to the Tarawa assault but lessons from this operation were subsequently incorporated. Earlier amphibious landings had been mostly conducted against large hilly and forested islands against limited or no resistance. The lessons learned in the Tarawa assault, a small atoll island ringed with strong defenses, were critical: particularly those pertaining to using amphibian tractors to attack across broad coral reefs. This was the first assault in which amphibian tractors (amtrac, landing vehicle, tracked LVT) were employed to deliver assault troops. They were previously used as cargo carriers. Other lessons were also learned, especially with regard to naval gunfire and aerial bombardment. Based on the experiences at Tarawa, it was realized the forces available for Flintlock might not be able to secure the proposed objectives. Operational planning was reevaluated, changes made, and less ambitious objectives assigned. On 7 December, Kwajalein became the primary objective and D-Day was set for 17 January. The revised plan, designated Flintlock II, was issued on 20 December. Admiral Raymond A. Spruance, Commander, Central Pacific Forces and Fifth Fleet, expressed concerns that Kwajalein was located deep within the Japanese defenses, preferring Wotje and Maloelap to be secured first. Nimitz soon recommended the target date be changed to 31 January. The Joint Chiefs of Staff insisted the operation commence in January, but the landing forces could not be ready by the original 17 January date. Admiral Spruance, still concerned about bypassing the outer bases, requested that Majuro Atoll to the east be secured. It was either lightly or undefended and would provide airfields to protect Kwajalein from Japanese forces on Jaluit, Maloelap, Wotje, and Mille. It would also serve as a fleet anchorage. The 106th Infantry was assigned to the operation and a reinforced battalion tasked to secure Majuro. A further delay was requested, to 10 February, to allow the divisions to fill equipment shortages and permit the 4th MarDiv to conduct a full rehearsal. This request was denied.

The other bases were to be neutralized by air and naval bombardment through the campaign. Eniwetok in the extreme northeast of the Marshalls would receive particular attention, as it was key to the aerial supply route from Japan. It would be seized later in the operation to block this flow. Once the objectives were secured they would be developed to provide staging and supporting bases for the Western Pacific drive. The bypassed islands would continue to be neutralized from the new American bases established on the captured atolls.