patrol actions. The first shot of the war at sea was fired on 5 August1914 by a destroyer of the 3rd Flotilla, Lance, in an engagement with the German auxiliary minelayerKönigin Luise. The first British naval casualty was Amphion, the light cruiser leading the 3rd Flotilla, which ran into a mine laid by Königin Luise.

Destroyers were involved in the skirmishes that prompted the Battle of Heligoland Bight, and filled a range of roles in the Battle of Gallipoli, acting as troops transports and fire support vessels, as well as their fleet-screening role. Over 80 British destroyers and 60 German torpedo-boats took part in the Battle of Jutland, which involved pitched small-boat actions between the main fleets, and several foolhardy attacks by unsupported destroyers on capital ships. Jutland alsoconcluded with a messy night action between the German High Seas Fleet and part of the British destroyer screen.

The threat evolved by World War I with the development of the submarine, or U-boat. The submarine had the potential to hide from gunfire and close underwater to fire torpedoes. Early-war destroyers had the speed and armament to intercept submarines before they submerged, either by gunfire or by ramming. Destroyers also had a shallow enough draft that torpedoes would find it difficult to hit them.

The desire to attack submarines underwater led to rapid destroyer evolution during the war, which were quickly equipped with strengthened bows for ramming, depth charges and hydrophones for identifying submarine targets. The first submarine casualty to a destroyer was the German U 19, rammed by Badger