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The storm landings on Kwajalein and Eniwetok benefitted from a number of lessons that were learned at great cost in the preceding Operation Galvanic, the seizure of the Gilberts, which culminated with the assault on Tarawa Atoll.
Of the many lessons absorbed by US commanders, the first was a greater appreciation for the ingenuity and durability of Japanese military engineering to be encountered in the Central Pacific.
The all-too-brief three hours’ pre-invasion bombardment by the task force failed to eliminate concrete emplacements housing artillery from 3 to 8 inches in caliber, as well as the more numerous concrete and coconut log pill boxes and bunkers dotting the island.
The decision to use high explosive ordnance with instantaneous fuses proved inadequate to the task, even failing to collapse the rich system of trenches and anti-tank ditches connecting the emplacements housing MGs and artillery.
The beach defenses themselves—bunkers giving enfilade to wire and log fences emplaced on the coral reefs—proved particularly robust and contributed to heavy losses among the first and second waves of assault troops.
In order to avoid the cost of another Tarawa, great care was taken to prepare the islands in the Marshalls targeted for assault. This included allowing three days’ intense preparation by naval and air assets before the landing force set out for the beach.
Naval gunnery ranges were shortened to improve accuracy, with a mixture of high-explosive and armor-piercing munitions; delay-action fuses now accounted for 60% of all types of ordnance used. In addition, nearby islets were utilized as artillery platforms to support the attack.
The large number of well-constructed concrete air raid shelters revealed that the enemy’s main concern was not an attack from the sea. The absence of offshore mines and obstacles of the type encountered on Tarawa were gratefully noted. Anti-tank obstacles were encountered.
The relative ease with which Jap. defenses were overcome on Kwajalein led to a shortened period of preparation for the Eniwetok assault. As a result, the largely below-ground defensive network relied on by the Jap. was unscathed and contributed to the higher casualty list.
Nonetheless, the interior of both Kwajalein and Eniwetok were marked by extensive trench systems connecting a network of gun emplacements, rifle pits, and bunkers housing MGs. Heavy ordnance, particularly dual-purpose 5” guns and AAA were reduced in capability by the
pre-invasion bombardment.
Ironically, post-battle examinations of enemy fortifications showed that the defenses on Kwajalein would have been subdued by the type of quick bombardment that failed on Tarawa.
Ironically, post-battle examinations of enemy fortifications showed that the defenses on Kwajalein would have been subdued by the type of quick bombardment that failed on Tarawa.
That Japanese defensive preparations were considerably weaker in the Marshalls was not a reflection of a failure to anticipate an attack from the sea. A captured report revealed that indeed the Jap. were aware of the growing danger to its possessions in the Marshalls
and were in the beginning phases of improving defenses when US forces appeared over the horizon.
The primary difference between Kwajalein and Eniwetok defenses lay in the former’s reliance on above-ground field fortifications and 5” guns to defend against naval attack.
The primary difference between Kwajalein and Eniwetok defenses lay in the former’s reliance on above-ground field fortifications and 5” guns to defend against naval attack.
This made Kwajalein more vulnerable to the extensive period of air and naval attack preceding the landings. Eniwetok’s defenses, as noted, were a superb case of groundhog work, all sited within 50 yards of the high water line.
Both the US Army and Marine Corps endorsed the delivery of medium armor (M4 Shermans) directly to beach with the first wave to provide suppressive fire to bunkers and pillboxes sited at the high water line. Light armor was recommended for the exploitation phase of the battle.
