The Destroyers for Bases Agreement was finalised between Winston Churchill and Franklin Roosevelt in September 1940, and fifty ageing American destroyers were transferred to the Royal Navy as the , in return for bases across the empire. As part of the deal four hundred American technicians were transferred to HMS Ferret, arriving on 30 June 1941 and started working in civilian clothes as America was not officially at war. The American personnel later moved out of Ferret and into camps constructed in the area, and on 5 February 1942 a US base was officially established. US Marines also arrived, and were used to guard the camps and the main base, as well as outlying ammunition dumps. In November 1942 Eleanor Roosevelt visited the base, accompanied by Lady Montgomery, the mother of Field Marshal Bernard Montgomery.
