What was the Japanese military code name for the Pearl Harbor attack?

The Japanese military code name for the Pearl Harbor attack was Operation Z.

The designation was used in Japanese planning documents and communications for the carrier strike against the U.S. Pacific Fleet. Admiral Isoroku Yamamoto supported the operation as a way to weaken American naval power before Japan expanded its war in the Pacific.

The attack plan involved a long-range carrier force sailing across the North Pacific while maintaining radio silence. Japanese planners hoped that a surprise blow against the battleships and airfields would delay American intervention in Japan’s broader strategic campaign.

Operation Z should not be confused with the Japanese operation against the Soviet Union called Kantokuen or with later Japanese operations in the Pacific. In English-language histories, “Pearl Harbor attack” remains the usual description, while “Operation Z” identifies its Japanese planning code.