Adding Russia breaks the Washington treaty hierarchy

Britain and the United States might accept equality with one another but not with Russia. Japan would reject formal inferiority to the rival it defeated in 1905, while Russia would insist that a rematch required equality with Japan. France would resist falling below its Russian ally, and Italy would demand whatever status France received. A collective-security clause promising joint action against an aggressor might make parity safer in practice. It would not remove the prestige fight or the economic burden created when four second-rank powers all claim the same large capital-ship allowance.