At dawn on 20 November 1943, U.S. marines launched an assault on Tarawa, a Japanese-held atoll in the British Protectorate of the Gilbert and Ellice Islands. The water in the lagoon was only 3 feet deep that morning, less than the 4–5 feet required by a fully loaded personnel carrier to navigate the waters. As a result, marines saddled with equipment were forced to wade almost a mile across the lagoon under heavy Japanese fire. The United States won the Battle of Tarawa, but it proved to be one of the bloodiest battles of the war; almost 6000 Japanese, Americans, and Gilbertese were killed in just 3 days of fighting. Of the American fatalities, almost half occurred because U.S. military planners ignored warnings about the local tides on the morning of the assault [e.g., Wright, 2000].