Treaty-era modernisation of capital ships

The Washington and London treaties kept older battleships and battlecruisers in front-line use longer while air and underwater attack made them less acceptable in modern war. Treaty rules allowed limited defensive modernisation, but money and stability restricted what could be done at once. Bulges had to come first because their additional buoyancy and stability supported the topweight of later deck armour. This sequencing reduced immediate cost but postponed part of the protection programme until further funds became available. Anti-aircraft defence and collective gas protection competed for attention within the same constrained refits. The named schedule of ships from Royal Oak through Barham shows that fleet modernisation was a long programme of priorities rather than a single uniform upgrade.