Tregantle Fort was completed in 1865 with barracks accommodation for 1,000 men and provision for 35 large guns. In the event, far smaller establishments have been based there, with only six gunners in 1882. In 1893 the guns consisted of five RBL 7 inch Armstrong guns and nineteen RML 64-pounders, together with a number of SBBL 32-pounders being tested. Tregantle was vacated after World War I until 1938, when it was used as the Territorial Army Passive Air Defence School. During World War II it was used first as the Army Gas School and from 1942 as US Army accommodation.