Why naval unit sizes change between wars

How do squadrons, divisions, and flotillas relate to one another?

Their sizes depend on each navy's organization and wartime realities; they are functional groupings rather than fixed universal numbers.

An eight-ship battle squadron might divide into four-ship divisions, but those numbers were not universal definitions. Organization tables depended on the navy's available ships and the firepower commanders wanted to control as a unit. A Royal Navy destroyer flotilla could include about twenty destroyers and several light cruisers in the First World War. By the Second World War and during its attrition, the practical formation shrank toward eight and sometimes four destroyers.