#OTD January 31, 1944 the battles of Kwajalein and Majuro atolls begin. Operation Flintlock—the seizure of the Marshall Islands—followed quickly on the success of Operation Galvanic, furthering US advances in the Central Pacific.

RADM Richmond Kelly Turner’s Fifth Fleet Amphibious Force, seasoned in its first storm landing at Tarawa the previous November, profited from experience in that operation by adjusting its tactics to ensure a higher degree of suppression of the Japanese defenses on the island.

Utilizing armor-piercing rounds (high-explosive rounds had been employed at Tarawa, to little effect) fired from much closer ranges, a higher degree of survivability was ensured among the assault force drawn from MG Holland M. Smith’s V Amphibious Corps.

In addition to shifting its bombardment tactics to account for lessons learned at Tarawa, the success of LVT amphibious tractors surmounting the coral reefs at Betio called for the strengthening of their available number.

The more numerous LVT A-2 were modified to carry troops, while the LVT A-1 would be employed as a fire-support weapon; its .50 caliber machine guns providing suppressing fire in support of the assault force.

To increase the amount of available firepower to support the landings, 24 Landing Craft Infantry (LCI) were modified as gunboats. The LCI’s bristled with a variety of .50 cal. machine guns, 40- and 22-mm cannon, and rockets that would land in a curtain ahead of the infantry.

Smith’s assault force, which comprised the Fourth Marine and US Army 7th Infantry divisions, would first seize smaller barrier islands neighboring Kwajalein for use as artillery platforms to support the main assault.

The undefended island of Majuro offered an impressive lagoon for use as an anchorage to support further advances into Central Pacific, while Roi-Namur, the hub of Japanese air operations in the region, was prized for its airfield—most atolls were too small to support airfields.

In concert with the Fifth Fleet’s Southern Attack Force and long-range attacks by USAAF B-24 bombers, the assault on Kwajalein began on February 1, 1944 with the landing of the 22nd Marine Regiment on Roi-Namur.

Three days of sustained bombing had eliminated Roi’s complement of 83 aircraft. The fire support plan more than doubled the weight of heavy-caliber shells to prepare the island for assault. Fifth Fleet battleships dumped over 6,000 shells on Roi.

Originally perceived as a tougher nut to crack than Tarawa had been, the assault force approached the island from the direction of its lagoon, taking Japanese defenses from the rear. Despite bitter resistance, the island of Roi was secured by 1400 hours on February 2.

The army’s landings on Kwajalein Atoll benefitted from the same tactical adjustments that made the seizure of Roi-Namur a success. Although fighting would continue until 7 February on Kwajalein, the lessons of Tarawa saved many lives and refined US amphibious tactics.

The stunning success of Operation Flintlock opened the way to the next major advance in the Central Pacific towards the Marianas Islands and fast carrier forces joining the fleet now had a robust anchorage to support raids deep into enemy held territory. #WWII #SWW