Short answers, pulled from the story.
The United States Pacific Fleet and Marine Corps began their first large-scale offensive across the Central Pacific in August 1942. This operation aimed to establish airfields and naval bases to support future military actions.
Keiji Shibazaki commanded 4,836 troops including construction workers on Tarawa. He oversaw over 100 machine gun nests and 500 pillboxes while defending Betio island with a large wall across the northern lagoon.
American forces seized Tarawa from nearly 5,000 Imperial Japanese Naval Landing Forces between 20 and the 23rd of November 1943. The fighting lasted three days and resulted in heavy American casualties due to poor coordination between naval bombardment and ground troops.
Out of roughly 3,000 Japanese soldiers stationed at Kwajalein, only about 300 remained to contest the landing. Major General Harry Schmidt led the 4th Marine Division against Roi-Namur islands starting on the 31st of January 1944.
Eniwetok Island was captured on the 21st of February 1944 after Lieutenant General Thomas E. Watson led the 106th Infantry Regiment onto the main island. Americans attacked mainly at night during this phase while facing Japanese spider holes and bunkers that withstood much shore bombardment.