Tarawa Atoll is a series of small islands in the Gilberts. The major Japanese outposts were on Betio, a bird-shaped island in the southern part of the chain; and Makin, which was raided early in 1942 by US Marines. Nine leathernecks who were mistakenly left behind were executed, but the raid was considered a success, especially by a victory-starved American public.
After the Battle of Midway and especially after the fall of Guadalcanal, the Japanese Imperial Navy began to fortify the Gilberts. Rear Admiral Keiji Shibasaki, commander of Betio, received four of the heavy guns from Singapore that the British hoped would turn back an invasion. Shibasaki announced that a million men could not take Tarawa in a hundred years." It would take 35,000 men four days to conquer Tarawa; at the end of the battle, neither side would look at the war the same way.
Tarawa was far more heavily fortified than any island the Allies had encountered before; to attack it the growing strength of the United States Navy would mobilize a fleet of dozens of ships. On November 22, 1943, after a three-hour bombardment, the 2nd Marine Division landed on Betio. Shibasaki had 2500 Imperial Naval Marines, with 2,300 Korean and Japanese laborers. They had transformed Betio into a fortress of unparalleled intricacy, with coconut log bunkers cemented with crushed coral and intersecting zones of fire. The fire thrown against the US Marines was intense, and within the first hour the first wave had suffered almost total casualties. The amtracs, mobile personnel carriers that could operate on land and water, were in high demand by Americans, but were being destroyed one by one.
In contrast, the landings on Makin had much lower casualties for the Americans. The smaller garrison died almost to a man. Additional landings on smaller islands in the Gilberts were accomplished by submarine.