What war-emergency ship classes did the main World War I naval powers build?
Short answerThe Royal Navy's Flower-class sloops are the clearest example, while US four-stack destroyers are a debatable case and monitors and other small vessels fit the pattern more generally.
NotesFlower-class sloops are the clearest British example, with merchant-influenced construction suited to rapid building, minesweeping, and other duties. American four-stack destroyers are a borderline case because of their higher standard, while monitors and small craft were the more usual emergency answer.