Admiral Isoroku Yamamoto

Truk was part of the Japanese Mandated Islands ceded to Japan in 1919. A major fleet anchorage was created there soon after occupation, and over the next twenty-five years the Japanese used Truk as their main base of operations for the Southern Pacific.

When Guadalcanal was secured, the Solomons were still largely held in Japanese hands or deserted. To the north, the major Japanese base on New Britain, Rabaul, could control the entire area with its large complement of aircraft and its excellent naval anchorage.

In April 1940, obsolescent British Swordfish biplanes, nicknamed "stringbags" for their flimsy construction, struck the Italian fleet at Taranto. Within minutes significant damage was done to Italy's Mediterranean Fleet. To get around the inability to operate torpedoes in the shallow waters of the harbor, the British attached fins to the tail.

With the attack on the United States Pacific Fleet on December 7, 1941, Japan had brought the most powerful nation on earth into the war on the side of the Allies.

The Imperial Japanese Navy (Nihon Kaigun) in 1941 was unquestionably a world power. With the help of the British, who trained the Japanese to the point that all bridge orders were issued in English, a Japanese fleet was built in the early twentieth century.