The First World War showed that submarines were powerful without proving that they were unanswerable. Convoy formations, hunter-killer groups, patrol aircraft, and ASDIC could detect a boat, force it down, or hold it away from shipping. Newspapers and politicians preferred a destroyed submarine because it produced a visible statistic, but escorts only needed the convoy to pass safely. A submarine prevented from attacking had suffered an operational defeat even when the boat survived.
Notable Point · 54:30-55:47
Convoys, ASDIC, and the real objective of anti-submarine warfare
Convoy routing and detection systems made it possible to defeat a submarine's mission without necessarily destroying the boat.