Chuuk Lagoon, Chuuk State, Federated States Of Micronesia, Pacific Ocean

The place was considered the most formidable of all Japanese strongholds in the Pacific. On the various islands, the Japanese Civil Engineering Department and Naval Construction Department had built roads, trenches, bunkers and caves. Five airstrips, seaplane bases, a torpedo boat station, submarine repair shops, a communications center and a radar station were constructed during the war. Protecting these various facilities were coastal defense guns and mortar emplacements. The Japanese garrison consisted of 27,856 IJN men under the command of Vice Admiral Masami Kobayashi then Vice Admiral Chuichi Hara and 16,737 IJA men under the command of Major General Kanenobu Ishuin. Due to its heavy fortifications, both natural and manmade, the base at Truk was known to Allied forces as "the Gibraltar of the Pacific".
A significant portion of the Japanese fleet was based there, with its administrative center on Tonoas (south of Weno). At anchor in the lagoon were the Imperial Japanese Navy's battleships, aircraft carriers, cruisers, destroyers, tankers, cargo ships, tugboats, gunboats, minesweepers, landing craft, and submarines. Some have described Truk as Japan's equivalent of the Americans' Pearl Harbor.
In 1944, Truk was devastated in one of the important naval attacks of the war. Forewarned by intelligence a week before the US raid, the Japanese had withdrawn their larger warships (heavy cruisers and larger vessels) to Palau. Once the American forces captured the Marshall Islands, they used it as a base from which they launched an early morning attack on February 17, 1944 against Truk Lagoon. Operation Hailstone lasted for three days, as American carrier-based planes sank twelve warships (light cruisers, destroyers, and auxiliaries) and thirty-two merchant ships, while destroying 275 aircraft. The consequences of the attack made "Truk lagoon the biggest graveyard of ships in the world".
The attacks for the most part ended Truk as a major threat to Allied operations in the central Pacific; the Japanese garrison on Eniwetok was denied any realistic hope of reinforcement and support during the invasion that began on February 18, 1944, greatly assisting U.S. forces in their conquest of that island. Truk was isolated by Allied (primarily U.S.) forces as they continued their advance towards Japan by invading other Pacific islands such as Guam, Saipan, Palau, and Iwo Jima. Cut off, the Japanese forces on Truk and other central Pacific islands ran low on food and faced starvation before Japan surrendered in August 1945.