Short answers, pulled from the story.
The Gilbert and Marshall Islands campaign was a series of U.S. military engagements fought from August 1942 to February 1944 in the Pacific theatre against Japan. It was the first large-scale American offensive across the Central Pacific, aimed at capturing Japanese-held atolls to establish airfields and naval bases for further operations.
The Battle of Tarawa was fought from the 20th to the 23rd of November 1943. The Americans suffered a total of 2,459 dead and 2,286 wounded across the entire Gilberts campaign, while Japanese losses reached 5,085 dead and only 247 captured.
Admiral Keiji Shibazaki commanded 4,836 troops on Tarawa, including around 2,600 Special Naval Landing Forces, approximately 1,000 Japanese construction workers, and 1,200 Korean laborers. He concentrated his defense on Betio island, which held the atoll's airfield.
Allied intelligence intercepted and decrypted Japanese transmissions revealing that Admiral Mineichi Koga had concentrated his 28,000 troops in the outer islands of Maloelap, Wotje, Jaliuit, and Mili. The Americans therefore targeted the comparatively lightly defended but strategically important atolls of Majuro, Kwajalein, and Eniwetok instead.
After Tarawa, American commanders ensured they outnumbered Japanese defenders by nearly 6 to 1 at Kwajalein, brought heavier firepower including armor-piercing shells, and subjected target islands to nearly a month of combined air and naval bombardment before landing troops. These changes contributed to far lower American casualties in the Marshall Islands.
The Battle of Eniwetok ended on the 23rd of February 1944 when the entire atoll was secured. Across the Eniwetok operation, 313 Americans were killed, 879 wounded, and 77 reported missing, while the Japanese suffered 3,380 dead and 105 captured.