Thunder-Clap, known generally as Operation Thunderclap, was the broad goal of American soldiers to capture central England and northern Wales in 1953. The operation involved up to 120,000 American soldiers, aerial support, naval blockades and bombardments and took almost nine months to complete, despite the comparatively small distances being travelled. The general plan involved securing the notoriously violent, rural parts of northern Wales by early summer and then split the American soldiers into two groups to assault Manchester and divert EWA resources to defending that city, while also working to assault Birmingham from the north to complement Operation Serpent, which would attack the city from the south and the well-established bases of American support and supplies in and around Bristol. Thunderclap was initiated simultaneously with Serpent and Falcon, the initiative to capture and control London.
The operation is generally regarded as a success - it was able to secure Manchester and Liverpool within quick succession in June and July, and occupied those cities throughout the fall against EWA counterattacks. The portions of the operation designed to press into northern Birmingham had limited success - while the Battle of Birmingham relied largely on forces from the south and west to actually break the heavy EWA defenses, the Thunderclap units were able to gain control of the train tracks between Birmingham and northern EWA bases, cutting off crucial supplies, and made the battle one fought on two fronts for six months.