Deterrence required both persistent patrols and a credible heavy force

Persistent patrols were the visible layer of deterrence, backed by a smaller force of trained heavy units able to reinforce the warning. Those large ships did not need to be numerous, but they had to remain ready and available. Success would usually appear as an absence of naval war. The late nineteenth-century Royal Navy illustrates this assessment: worldwide presence backed by battleships or large ironclad frigates made a naval challenge unattractive. British trade also drew strength from the merchant navy, insurance, and banking industries. A relatively small British army still left land warfare a different proposition, so the argument concerns deterrence at sea.