The London treaty's existing fault lines

Japan accepted the London limits while preparing its infrastructure for the greater freedom it expected after 1936. Planning for war in the following decade was already making the Ten Year Rule assumption harder to sustain. France resisted cumulative limits that would force it to choose between balancing Italy in the Mediterranean and protecting worldwide commitments. Italy, in turn, would not accept less than France, while Britain could not ignore unrestricted Italian growth along its principal imperial trade route. French and Italian exemptions therefore required escalator clauses that could release other powers from their totals if construction grew too far. Exceptions for vessels such as the French submarine Surcouf also protected particular capabilities. These linked concessions made the historical treaty difficult to negotiate before a Soviet delegation added another set of demands.