the division's commanders. Japanese preparations Located about southwest of Pearl Harbor, Betio is the largest island in the Tarawa Atoll. The small, flat island lies at the southernmost reach of the lagoon, and was the base of the majority of the Japanese troops. Shaped roughly like a long, thin triangle, the tiny island is approximately long. It is narrow, being only wide at its widest point. A long pier was constructed jutting out from the north shore, onto which cargo ships could unload cargo while anchored beyond the -wide shallow reef which surrounded the island. 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 Colonel Evans 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 reinforced the island in February 1943. In command was Rear Admiral Tomonari Saichirō (友成 佐市郎), 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. Tomonari'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 pillboxes 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 interior. The interior structures were large and vented, but did not have firing ports. Defenders were limited to firing from the doorways. The Japanese worked intensively 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 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