By fall 1943, Japanese forces had been ejected from Alaska’s Aleutian Islands in the North Pacific, and the Solomon Islands in the South Pacific were on the verge of capture.
US forces now had to push into the Central Pacific, from which they could target Japanese strong points and communications lines. US officials had spent much of that year preparing for Operation Galvanic — the capture of the Gilbert Islands, a group of coral atolls that are now part of Kiribati.
Held by the British until Japan seized them in December 1941, the Gilberts were “of great strategic significance because they are north and west of other islands in our possession and immediately south and east of important bases in the Carolines and Marshalls,” US Navy Fleet Adm. Ernest J. King wrote in official reports.
“The capture of the Gilberts was, therefore, a necessary part of any serious thrust at the Japanese Empire.”
The attack on Tarawa focused on Betio, the principal island in the atoll, located at its southwest corner.
“The island was the most heavily defended atoll that ever would be invaded by Allied forces in the Pacific,” historian and Marine amphibious officer Joseph Alexander wrote.
US Marines stormed ashore Betio on November 20, 1943. After 76 hours of intense fighting, they had wrested it away from tenacious Japanese defenders.
US planes had done reconnaissance of Betio and Tarawa since the beginning of 1943. In August 1943, Vice Adm. Raymond Spruance, commander of the US Central Pacific Force, verbally assigned the capture of Tarawa Atoll to the Second Marine Division. In mid-September, Navy and Army planes bombed and photographed the atoll.
Tarawa is a coral atoll roughly triangular in shape. Its east side is about 18 miles long, while the south side is 12 miles long and the west side 12.5 miles long. The string of islands that make up the atoll ranged in altitude from 8 to 10 feet and were covered in coconut trees and dense shrubs. Betio is a bird-shaped island at the atoll’s southwest corner that at the time had an area of about 300 acres.
Japanese commanders concentrated their forces on Betio, a strongly defended island at the southwest corner of the atoll, planning to destroy US transports at sea and then “concentrate all fires on the enemy’s landing point and destroy him at the water’s edge.” The island was estimated to have a garrison of 4,800 men — more than half of them first-rate troops.
Betio’s defenders deployed steel tetrahedrons, minefields, and and dense thickets of barbed wire. Walls of logs and coral surrounded much of the island. Machine guns, rifle pits, and antitank ditches were often integrated into the barricades, and many emplacements, like pillboxes, were built to have converging fields of fire.
Anti-personnel and anti-vehicle mines were scattered around the island, its lagoon, and its reef. Japanese forces on the island also had naval guns, coastal-defense guns, as well as field artillery and howitzers.
Source: US Marine Corps
Betio’s geography — narrow with no elevations higher than 10 feet — suited its defenders. “Every place on the island can be covered by direct rifle and machine gun fire,” Marine Col. Merritt Edison said. The island also lacked natural cover, and its tides and reef poised unique challenges.
The fight at Tarawa was the first large-scale encounter between US Marines and Japan’s Special Naval Landing Forces. Intelligence officers cautioned before the landing that “naval units of this type are usually more highly trained and have a greater tenacity and fighting spirit than the average Japanese Army unit.” Nevertheless, Marines were surprised at the intensity with which they fought.
Source: US Marine Corps