Why Japan sought a seven-to-ten naval ratio

The Japanese demand was presented as a security threshold rather than a belief that Japan could defeat either larger maritime power outright. A lower ratio encouraged designers to seek exceptional individual ships and reduced the perceived benefit of remaining inside the treaty system. A durable agreement therefore needed to leave every participant believing that compliance offered more security than withdrawal or concealment. Because British and American industrial capacity could eventually overwhelm Japan, the seven-to-ten ratio functioned as a hoped-for barrier against an easy initial victory rather than a claim to long-war equality.