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.