In the Battle of Tarawa (November 20-23, 1943) during World War II (1939-45), the U.S. began its Central Pacific Campaign against Japan by seizing the heavily fortified, Japanese-held island of Betio in the Tarawa Atoll in the Gilbert Islands. The 18,000 U.S. Marines sent to tiny Betio were expected to easily secure it; however, problems quickly arose. Low tides prevented some U.S. landing crafts from clearing the coral reefs that ringed the island. Japanese coastal guns pounded the snagged vessels and desperate Marines gave up on freeing the boats and instead waded toward shore–hundreds of yards away– through chest-deep water amidst enemy fire. Despite heavy resistance from the 4,500 Japanese troops dug in on Betio, the Marines finally took the island after a bloody, 76-hour battle in which both sides suffered heavy casualties.