Japan's seven-to-ten risk-fleet logic

Japan's desired seven-to-ten ratio was a deterrent calculation rather than a promise of outright victory. Japanese planners understood their industrial limits in a prolonged war against Britain or the United States, which helps explain their focus on short-war plans. Unlike Tirpitz's risk-fleet theory, this calculation did not depend on a third power exploiting the attacker's losses. Japan wanted an attack to cost enough that Britain or America would undertake it only with a strong reason. The fear was of suffering imperial intervention like that inflicted on China and other countries. The final 5:3 ratio largely preserved the existing balance, leaving Japan without the increase its leaders had sought.