Operation Iceberg, the US invasion of Okinawa, involved over 450,000 troops and 1200 transports in what was the largest naval operation mounted in the Pacific. About 130,000 Japanese troops defended the island from entrenched positions and they proved a formidable obstacle. Kamikaze attacks against the American naval forces also took a heavy toll. Almost all the Japanese defenders were killed, as well as about 42,000 of the 450,000 civilians on the island. Only 10,755 were taken prisoner. US casualties amounted to 12,500 killed and 35,500 wounded.