The vulnerability of
Japanese naval codes and ciphers was crucial to the conduct of
World War II, and had an important influence on foreign relations between Japan and the west in the years leading up to the war as well. Every Japanese code was eventually broken, and the intelligence gathered made possible such operations as the victorious American ambush of the Japanese Navy at
Midway (JN-25b) and the shooting down of
Isoroku Yamamoto in
Operation Vengeance.