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

As part of the colonial territory of the Caroline Islands, Truk was part of the Spanish Empire. The Caroline Islands control were sold to the German Empire in 1899. It became a possession of the Japanese Empire under a mandate from the League of Nations following Germany's defeat in World War I.
• World War II
During World War II, Truk Lagoon was the Empire of Japan's main base in the South Pacific theatre. Truk was a heavily fortified base for Japanese operations against Allied forces in New Guinea and the Solomon Islands, serving as the forward anchorage for the Japanese Imperial Fleet.
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".