Western Front
German infantry storm old Citadel, Boulogne. Guderian seals off Calais pocket. HITLER AND RUNDSTEDT HALT PANZER CORPS at Gravelines, southwest of Dunkirk.
French fortress of Maubeuge surrenders, after destruction of many reinforced concrete works by heavy artillery and demolition charges. Fall of Ghent and Tournai.
Sea War
British cruisers and destroyers give supporting fire in Calais sector. French destroyer Chacal bombed and sunk off Boulogne.
Air War
Scattered raids over Yorkshire, East Anglia and Essex (night May 24-25); 8 people injured at Middlesbrough – first civilian casualties in air-raid on England. RAF bomb Cologne marshalling yards (night May 24-25).
Secret War
British Government Code and Qypher School begins regular transmissions of decoded German Enigma messages to GHQ, BEF and RAF HQ in France.