World War I's submarine crisis shaped later Atlantic readiness

German submarine warfare came closer to defeating Britain in the First World War than in the Second. Britain entered the later conflict with earlier convoying, stronger escorts, and better anti-submarine capacity because the previous crisis remained in institutional memory. That preparation kept the dangerous periods of the Second World War from becoming as damaging as the earlier campaign. The comparison shows how a threat that succeeds once can face a much better prepared opponent the next time.