the imperial japanese navy was administered by the ministry of the navy of japan and controlled by the chief of the imperial japanese navy general staff at imperial general headquarters. in order to combat the numerically superior american navy, the ijn devoted large amounts of resources to creating a force superior in quality to any navy at the time. consequently, at the beginning of world war ii, japan probably had the most sophisticated navy in the world. betting on the speedy success of aggressive tactics, japan did not invest significantly on defensive organization such as protecting her long shipping lines against enemy submarines, which she never managed to do, particularly under-investing in anti-submarine escort ships and escort aircraft carriers.