As of 1989, it served NATO as a pre-positioned wartime ammunition depot, storing around 40,000 tons of missiles, depth charges, and conventional shells.

It was known as NATO Armament Depot Glen Douglas and was used for munitions storage by the Royal Navy, the United States and the Netherlands.

[4] In January 2003, the aircraft carrier HMS Ark Royal docked at the Glen Mallan jetty to stock up on supplies ahead of the impending invasion of Iraq.

With the tacit backing of trade union ASLEF, Motherwell based EWS drivers working on a MoD contract refused to transport munitions to the depot, in opposition to what they branded a "rush to war".

[6] The depot covers an area of 226 hectares (2.26 km2) and contains 56 magazines built into a hillside, capable of storing 40,000 cubic metres of conventional weapons, typically bombs, various types of ammunition, explosives and pyrotechnics.