The military needs large, secure spaces to assemble and stage its missions and supply lines, usually adjacent to airstrips. With the commencement of the Korean War in 1950, the Royal Canadian Air Force (RCAF) acquired the de Havilland lands and buildings and immediately set about constructing a supply depot that would serve the regular and reserve units in the region located at what is today 40 Carl Hall Road.
Created for the military, the Downsview Supply Depot currently provides space for film studios, the Merchants Market, and Downsview Park, among others
The Downsview Supply Depot is one of the largest such facilities the RCAF has ever built. The 7.5 hectare building constructed of reinforced concrete was completed in 1954. Cold war concerns about nuclear threats and bombings prevailed at this time, and so it is said that the building was designed to withstand the force of a ballistic missile attack. Housed beneath the supply depot is a stormwater reservoir that can hold more than four million litres which could be used for cleaning or putting out fires in the event of an attack.