Battle of Tarawa - Background

Background

In order to set up forward air bases capable of supporting operations across the mid-Pacific, to the Philippines, and into Japan, the U.S. needed to take the Marianas Islands. The Marianas were heavily defended. Naval doctrine of the time held that in order for attacks to succeed, land-based aircraft would be required to weaken defenses and provide some measure of protection for the invasion forces. The nearest islands capable of supporting such an effort were the Marshall Islands, northeast of Guadalcanal. Taking the Marshalls would provide the base needed to launch an offensive on the Marianas but the Marshalls were cut off from direct communications with Hawaii by a garrison and air base on the small island of Betio, on the western side of Tarawa Atoll in the Gilbert Islands. Thus, to eventually launch an invasion of the Marianas, the battles had to start far to the east, at Tarawa.

Following the completion of their campaign on Guadalcanal, the 2nd Marine Division had been withdrawn to New Zealand for rest and recuperation. Losses were replaced and the men given a chance to recover from the malaria and other illnesses that weakened them through the fighting in the Solomons. On July 20, 1943 the Joint Chiefs directed Admiral Chester Nimitz to prepare plans for an offensive operation in the Gilbert Islands. In August Admiral Raymond Spruance was flown down to New Zealand to meet with the new commander of the 2nd Marine Division, General Julian Smith, and initiate the planning of the invasion with the division's commanders.

Located about 2,400 miles southwest of Pearl Harbor, Betio is the largest island in the Tarawa Atoll. The small, flat island lies at the southern most reach of the lagoon, and was home to the bulk of the Japanese defenders. Shaped roughly like a long, thin triangle, the tiny island is approximately two miles long. It is narrow, being only 800 yards wide at the widest point. A long pier was constructed from the north shore from which cargo ships could unload out past the shallows while at anchor in the protection of the lagoon. The northern coast of the island faces into the lagoon, while the southern and western sides face the deep waters of the open ocean.

Following Carlson's diversionary Makin Island raid of August 1942, the Japanese command was made aware of the vulnerability and strategic significance of the Gilbert Islands. The 6th Yokosuka Special Naval Landing Force arrived to reinforce the island in February 1943. In command was Rear Admiral Tomanari Sichero, an experienced engineer who directed the construction of the sophisticated defensive structures on Betio. Upon their arrival the 6th Yokosuka became a garrison force, and the unit's identification was changed to the 3rd Special Base Defense Force. Sichero's primary goal in the Japanese defensive scheme was to stop the attackers in the water or pin them on the beaches. A tremendous number of pill boxes and firing pits were constructed with excellent fields of fire over the water and sandy shore. In the interior of the island was the command post and a number of large shelters designed to protect defenders from air attack and bombardment. The island's defenses were not set up for a battle in depth across the island's interior. The interior structures were large and vented, but did not have firing ports. Defenders in them were limited to firing from the doorways.

The Japanese worked intensely for nearly a year to fortify the island. To aid the garrison in the construction of the defenses, the 1,247 men of the 111th Pioneers, similar to the Seabees of the U.S. Navy, along with the 970 men of the Fourth Fleet's construction battalion were brought in. Approximately 1,200 of the men in these two groups were Korean forced laborers. The garrison itself was made up of forces of the Imperial Japanese Navy. The Special Naval Landing Force was the marine component of the IJN, and were known by US intelligence to be more highly trained, better disciplined, more tenacious and to have better small unit leadership than comparable units of the Imperial Japanese Army. The 3rd Special Base Defense Force assigned to Tarawa had a strength of 1,112 men. They were reinforced by the 7th Sasebo Special Naval Landing Force, with a strength of 1,497 men. It was commanded by Commander Takeo Sugai. This unit was bolstered by 14 Type 95 light tanks under the command of Ensign Ohtani.

A series of fourteen coastal defense guns, including four large Vickers 8-inch guns purchased during the Russo-Japanese War from the British, were secured in concrete bunkers and located around the island to guard the open water and the approaches into the lagoon. It was thought these big guns would make it very difficult for a landing force to enter the lagoon and attack the island from the north side. The island had a total of 500 pillboxes or "stockades" built from logs and sand, many of which were reinforced with cement. Forty artillery pieces were scattered around the island in various reinforced firing pits. An airfield was cut into the bush straight down the center of the island. Trenches connected all points of the island, allowing troops to move where needed under cover. As the command believed their coastal guns would protect the approaches into the lagoon, an attack on the island was anticipated to come from the open waters of the western or southern beaches. Kaigun Shōshō Keiji Shibazaki, an experienced combat officer from the campaigns in China relieved Sichero in July 20, 1943 in anticipation of the coming combat. Shibazaki continued the defensive preparations right up to the day of the invasion. He encouraged his troops, saying "it would take one million men one hundred years" to conquer Tarawa.