As shown in the Spanish Civil War, the Luftwaffe were more than capable of accurately bombing many of Britain's key installations, which were also undersized to meet forecast required volumes.
The site chosen was farmland next to the Great Western Railway South Wales Main Line, which offered additional benefits.
This included a marshalling yard at the main site, sidings at Brackla Ridge, and the construction of Tremains halt near Waterton for worker access.
Gee Walker & Slater Ltd, and Sir Lindsay Parkinson & Co. Ltd were the contractors awarded the project to build ROF 53.
By 1940, the sites were in full production, with nearly 40,000 people working at the factory, the largest single-site employer in the country.