Operation Hailstone, 17-18 February 1944: the Task Force 58 raid on the Japanese fortress of Truk

Diver Rod Macdonald describes the underwater remains of a Pacific War battle that resulted in the largest two-day loss of shipping of WWII.

Chuuk Lagoon, as Truk Lagoon has been known since 1990, is a great natural harbour ringed by a barrier reef some 140 miles in circumference and 40-50 miles in diameter. It is one of the many lagoons and atolls that make up Chuuk State.

Rising up from the deep blue oceanic depths of the western Pacific, Chuuk State is one of the four Federated States of Micronesia – along with Yap, Pohnpei, and Kosrae – which together comprise some 607 islands scattered over almost 1,700 miles just north of the equator to the north-east of New Guinea.

During the 1920s and ’30s, Japan had developed Truk in secret as a powerful naval and air base. By the start of WWII in 1939, Truk had become the Imperial Japanese Navy’s Fourth Fleet Base, and from 1942 to 1944 it was the Japanese Combined Fleet’s main forward naval base in the Pacific.

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