[2] The construction of the base started in July 1941, in response to American expectations that they would be shortly entering World War II.

[1] The castle and estate was sold in early 1940, ending 500 years of Clan Campbell ownership of Rosneath and the surrounding area.

[1] Although shiploads of construction machinery arrived from the US,[3] work was delayed due to the lack of a rock crusher, which meant the local quarry, which was 25 miles away, needed to be used for the delivery of aggregate.

They also built a laundry and roads to service the area as well as renovating a number of buildings to provide a hospital and admin offices.

[1] On 20 August 1943, the base was again reactivated by the United States Navy, to act as the main receiving station for personnel who needed to be assigned to a specific vessel or location.

[1] During that year, up until August 1944, thousands of men arrived from the US, to be transferred to duties on ships and naval bases that were located all over the UK.

[1] The base provided training, supply and maintenance crews for increasingly larger units as the war progressed, including the 11th Amphibious Force consisting of 1900men.

[1] The base also included: Slightly north of Rosneath was Camp Clachan that consisted of barracks and facilities for 400 men and used to house the 29th Seabees.

A hospital was also constructed on a hillside overlooking the Firth of Clyde and contained 680 beds, designed in a fan shape with a galley at the centre.