Description:"U-boat's commander" (actually RN) takes bearings before submerging. Medium shot of periscope cutting the water as the U-boat approaches its "helpless victim". Merchantman sights U-boat (now surfaced), and sends SOS to fleet - cut to medium long shot across fleet anchorage, taken from HMS Canada (cf THE EMPIRE'S SHIELD, IWM 551). PC boats leave harbour. Smokescreen laid to cover their manoeuvres. Inboard medium shot as hydrophone gear is hoisted out and lowered into the sea. Close-up of operator. Destroyers in line ahead hasten to the scene (cf IWM 551). Long shot as British "submarine cruiser" (K Class) appears towing CB airship. Various aerial and surface views as smoke bombs are dropped to screen approaching destroyers. Aerial and inboard views of a destroyer dropping depth charges. Submarine conning tower breaks the surface, and the crew abandons ship. Patrol craft lower boats to rescue survivors. Airship SS23 is returned to its shed after a successful day. PC boats return to harbour. Final titles show the numbers of U-boats destroyed each year, 1914-18, demonstrating the growing efficiency of British ASW forces. End medium shot silhouette of London Class battleship.
Review of anti-submarine warfare (ASW) techniques, and a tribute to the British scientists who devised the instruments which defeated the U-boat.
Mots-clés:EFG1914 / World War I / Royal Navy, CANADA (HMS), battleship / Royal Navy, Charing / Royal Navy, Trego / Royal Navy, PC43 / ships, British naval - special operations: PC43 (Q-ship) / ships, British naval - special operations: Charing (Q-ship) / ships, British naval - special operations: Trego (Q-ship) / ships, British naval - escort: PC43 / ships, British naval - battleship: London Class / ships, British naval - submarine: K Class / aircraft, British naval - airship: SS23 / combat [simulated], British naval - anti-submarine / equipment, British naval - surveillance: hydrophone / equipment, British naval - surveillance: periscope / weapons, British naval - CBW: smokescreen / weapons, British naval - depth charge / propaganda, British - inspirational / 12/3(261.2).011