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The Gilbert and Marshall Islands were key points in the defensive perimeter that the Japanese set up around their newly conquered Pacific empire in 1942, occupying the eastern tip of the Empire in the Central Pacific. They had been expected to one of the first American targets during any war against Japan, but the unexpected campaigns in New Guinea and the Solomon Islands delayed that counterattack. The Americans were finally ready to strike late in 1943, marking the start of Nimitz’s Central Pacific offensive. This book looks at some of the battles during the brief campaigns in the Gilberts and Marshalls, where the first gaps were blasted in that defensive perimeter.
Once nice feature of the campaign map is that the islands captured by the US by 25 February 1944 and those held by the Japanese to the end of the war are clearly marked. One clear difference between the two campaigns is that in the Gilbert Islands the Americans attacked the main Japanese defended position on Tarawa, while in the Marshalls they bypassed the key Japanese defensive positions at Wotje, Maloelap, Mille and Jaluit in the east and south of the island group and instead focused on Kwajalein and Eniwetok in the centre and west of the group.
We start with a look at pre-war American doctrine for amphibious warfare. American plans for a war with Japan assumed that they would have to seize some of the Japanese held islands in the Marshalls, Carolines and Paulau Islands in order to allow their fleet to safely operate in the western Pacific. As a result a great deal of effort went into planning for amphibious warfare, so when the need for it finally came detailed plans already existed for ship to shore movement, timing of attack waves, naval gunfire support etc.
One of the key elements in the Japanese plan for the war was the idea of creating a large defensive perimeter that would keep the fighting at a safe distance from Japan and force the Americans to exhaust themselves attacking a series of heavily defended islands. This turned out to have two major flaws. The first was that as the attackers the Americans were able to choose where to strike next, and could concentrate overwhelming force against each island in turn. The Japanese were well aware of this problem, and the defensive doctrine in place during these battles was based around the idea of defeating a stronger attacking force, ideally before they could actually land, if that failed by stopping them at the water’s edge and then with counterattacks to prevent a beachhead getting established. During these battles the Japanese Navy was unable to play its expected role in the defense of the islands, so the island defenders were left to fight isolated battles.
The second weakness was that the Americans could simply bypass many of the defended islands, leaving isolated Japanese garrisons with little or no ability to strike back.
We move on to a look at the ground forces involved in these battles. The US Marines are a familiar force, so the focus here is on the unit organisation in place in 1943 and how the units that took part in these battles were organised.
We get more detail on the Japanese side. This is because the Japanese garrisons were far more varied that the US attackers. Some islands were held by Special Naval Landing Forces, dedicated IJN ground forces that were first raised during the fighting in China, replacing landing forces taken from ships’ crews. However these were often short-lived units, and were unpopular within the Japanese Navy. As a result they were often filled with the lowest grade of conscripts or reservists, but they were trained in infantry fighting and like all Japanese units were determined defenders. Guard Units were formed to defend naval bases, and were similar to the SNLF. The Japanese expected everyone on an island to take part in the defence, so we also look at the Construction battalions, which were normally made up of a mix of Japanese and Koreans, the Special Base Units, and other impromptue defensive forces.
We then move onto the individual battles. At Betio the Japanase has a sizable garrison for the size of the island, and a good commander who had trained his men well, but who had made one mistake, assuming any invasion would come from the ocean side of the island. The initial bombardment destroyed many of the Japanese heavy weapons, and also killed the commander and most of his senior officers. The Japanese defensive plan didn’t work – the Americans weren’t stopped at the shoreline, there was no counterattack on D-Day, the defenders were soon split in two and the battle was over in a few days.
We then move on the Marshal Islands, and the invasion of Namur. This island was defended by 2,920 men, but 1,500 of them were from aviation units and 1,000 were civilians. Once again the defenses were posted on the ocean side while the invasion came on the lagoon side. The neighbouring island of Roi was captured in just six and a half hours. Namur was harder, but still only took two days. This was despite a fairly chaotic start, with the initial landings delayed by a lack of LVTs and some disorganisation. Once again the Japanese commanders were killed early, and there was thus little organised resistance (although individual Japanese strongpoints often fought hard).
The fight for Engebi in Eniwetok was even shorter. The rapid success at Kwajalein freed up the floating reserves, so the invasion was moved forward from May 1944 to 18 February. The island was defended by just over 1,000 men, the familiar mix of trained infantry, naval aviation units and civilians. However the commander on Engebi did learn from the previous invasions, and focused on the lagoon side of the island. There wasn’t the time or the materials to build strong pillboxes or bunkers, although plenty of trenches, dugouts and barricades were built. The island was hit by powerful air attacks several times before the actual invasion, destroying most of the above ground buildings, much of the ammo stocks and food. A massive naval bombardment began on 17 February, doing further damage to the defences. The island is a triangle, only one mile long on each side, so there must have been nowhere to hide. Once again there was no organised counterattack, and the battle was over in ten hours.
The most obvious conclusion to be drawn from this book is that these islands were essential undefendable. Low lying and flat, the defenders were thus unable to dig the sort of deep bunkers that would cause so many problems elsewhere. The Americans were able to contentrate overwhelming force – at Engebi the attack was supported by three battleships, three heavy cruisers, ten destroyers, six LCI(G)s, three escort carriers, one fleet carrier and two light carriers. With the main Japanese Fleet now being saved for the ‘Big Battle’ the US Navy was free to roam almost at will, leaving any Japanese held islands cut off and their garrisons trapped. Harder battles would come, on islands which offered more to the defenders, but the basic problems faced by the Japanese during these battles would never be solved.
Chapters
The Opposing Sides
Betio Island, Tarawa Atoll
Namur Island, Kwajalein Atoll
Engebi Island, Eniwetok Atoll
Analysis
Author: Gregg Adams
Edition: Paperback
Pages: 80
Publisher: Osprey
Year: 2023