During World War II he was appointed as executioner by the US Military and was responsible for 13 out of 16 hangings of US soldiers at the Shepton Mallet military prison in Somerset. In this capacity, Pierrepoint carried out executions not only for murder but also rape which, at the time, was a capital crime under US military law although not in British law. In six of these cases he was assisted by his nephew Albert - who was principal hangman for the remaining three executions.