OPERATION FLINTLOCK
31 JAN 1944 TO 3 FEB 1944

In the autumn of 1943 Japan was pushed on the defensive. During battles in the South Pacific it was facing heavy losses in the form of aircraft and vessels. On top of that, the Allies were slowly advancing up the Solomons Island chain and along the coast of New Guinea. Added to that a new front was building up in the Central Pacific. The only thing what the Japanese would need was time to rebuilt their forces. 

At this stage it was clear to Japanese Command, it could not defend everywhere, and as a result of that established a national defence zone. All areas in that zone, including Truk, were considered essential and were to be defended at all costs. Outside this area were New Guinea, the Northern Solomons, and the Bismarck Archipelago. The Japanese would give these up, but not without a fight! Prolonged resistance was needed in order to buy time and rebuilt forces. That this plan proved useless was demonstrated within months when Truk and Rabaul were "cancelled" with the stroke of one pen, and were not able to block the Allied advance through the Central Pacific. 

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Following the ditching of general MacArthur's offensive plan in the South Pacific, Admiral Nimitz' plan for the Central Pacific was in concept approved. Whilst the South Pacific theatre was still ongoing, the continued attack of the allies in the Central Pacific forced the Japanese to give up the defence of the South Pacific. They however, as was proven pretty fast later on, lost already too many resources to actually put up a proper defence in the Central Pacific. 

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After the capture of Gilbert Islands, Nimitz continued to move against the Marshall Islands. He was fully convinced of the weakness of the Japanese airpower in the Central Pacific, and pushed aside the fears of his commanders and went for the full centre attack.

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The battle of Kwajalein (31 Jan 1944 - 3 Feb 1944)- Operation Flintlock

The Kwajalein Atoll lays in the heart of the Marshall Islands. The island had been part of Imperial Germany after they were bought from Spain in 1899. At the end of WW1 they were assigned to Japan in the post war settlement through the South Seas mandate. The islands became a mistery to the outside world as the Japanese closed them for the outside world. Japan considered these islands as their outer defence ring. The strategic importance of these islands was recognized early on by the Allies as part of the Island Hopping strategy in a possible battle against Japan. Once the Japanese lost New Guinea and the Solomons they decided that both the Gilberts and Marhall islands were expendable, and us such started preparing for the defence closer to home. This didn't mean that they gave up the islands without a fight. The Marshall where reinforced by the Japanese at the end of 1943 to make their capture more costly for the Americans. By January 1944 the local commander in Truk, Admiral Masashi Kobayasi, has 28,000 troops to defend the Marshalls, but hardly any planes. 

The 6th Base Force under the command of Rear Admiral Monzo Akiyama was headquartered on Kwajalein since August 1941, was the main defence force of the islands. He had his man spread out thinly over the whole area with only naval-air bases on4 locations elsewhere in the  lagoon. The defence system was mainly in line with no in depth defence. The Japanese had twin 12.7cm guns to their disposal on each end of the island plus 80mm guns on the ocean and lagoon sides. The 22nd Air Flotailla, heavy depleted after the Gilbert campaign had 128 aircraft left in the Marshalls, of which only 10 on Kwajalein. 

Prior to the battle of Kwajalein a couple of more steps were taken, which consisted of continuous bombing of islands which could pose a threat to the upcoming operation. Once of the most significant milestones was the capturing of Majuro, which would serve as a forward naval base and to safeguard supply lines. Majuro was very lightly defended and the island was taken on 31 January 1944. 

The battle of Kwajalein started by various divisions, by capturing 4 small islands - which could be used as artillery basis for the next days assaults. As the islands were only 800m wide their could be no defence in depth and the Japanese planned for counter attacking the landing beaches. The only thing the Japanese didn't count on, was that the US Amphibian vehicles could cross the coral reefs and could land on the lagoon side of the Atoll, however the strongest defences faced the ocean, so such defence was horribly exposed. Added to this, the continuous bombardment by the Southern Attack force consisting of the USS Tennessee and b-24 Bombers and the artillery on earlier captured islands was devastating. A US soldier was quoted "the entire island looked like it was picked up and dropped from 20,000 feet.Even though the Japanese countered every night the island was declared secured by the end of the fourth day. 

On the North side of the atoll the troops followed a similar tactic. first capturing smaller islands, and then landing on the larger island Roi-Namur on 1 February 1944. The airfield here was captured quickly and the other half of the island was captured without too much resistance the next day. During the clashes there were not too many casualties on US side, with the unfortunate event happening when a marine demolition team threw a charge with explosive into a Japanese bunker, not realising that the bunker was actually a storage for torpedo warheads. The mistake killed 20 marines and wounded dozens more. An observing pilot radioed "the whole damn island has blown up!" 

The relatively easy capture of Kwajalein showed the US amphibious capabilities, and showed that enhanced training and tactics after earlier mistakes where indeed effective. (see battle of Tawara). 

The Japanese realised that the beach line defences were too vulnerable to naval and aerial bombardment. The lessons learned on Kwajalein were applied to the defences of the Mariana Island, and proved much harder.

The road to Truk now lay open.