With its prominent position overlooking the River Thames and the Houses of Parliament, Big Ben was a highly visible target for enemy aircraft during World War II. To prevent the bell tower's sounds from aiding enemy aircraft, the clock's chimes were silenced for the duration of the conflict.

While the clock tower (now the Elizabeth Tower) was a major target for the Luftwaffe, Big Ben’s bells did continue to chime throughout most of World War II. However, the clock faces themselves were not illuminated at night starting in September 1939 to comply with "blackout" regulations, preventing the tower from serving as a visual landmark for German bomber pilots during the Blitz. The chimes became a powerful symbol of British defiance and "The Sound of Freedom," as the BBC broadcast the live tolling of the hour to Nazi-occupied Europe at the start of every news program. There was a brief period between June and September 1944 when the live broadcasts were replaced by a recording; this was done because the sound of an explosion from a V-1 "Doodlebug" flying bomb during a live broadcast could have provided the Germans with immediate intelligence on the accuracy of their strikes. Despite the tower being damaged by a small bomb in May 1941, the Great Clock continued to keep time and the Great Bell never stopped striking the hours, standing as a resilient icon of the British spirit.