Following the ‘shell crisis’ of early 1915, and fearing prolonged dependence upon American sources of explosives, Britain’s newly created Ministry of Munitions decided to build on a green field site at Gretna, near the Solvay estuary, straddling the Scottish border with England, that would by 1916 become the largest explosives factory in the British Empire. Stretching 12 miles, and covering 30 square kilometres, this was to be for at least two years, possibly the largest green-field site factory complex in the world. The plant produced cordite, a propellant mixture of nitroglycerin and guncotton best described, in a phrase attributed to Sir Arthur Conan Doyle, as ‘devil’s porridge’. Built in record time, at a cost of over £9 millions, and eventually employing over 30,000 workers, Gretna became a symbol of Britain’s approach to industrial warfare, and of its determination to achieve ‘chemical independence’ from Germany, and also from its allies. Thanks to contemporary visits of Rebecca West and others, the factory’s role in the struggles of the ‘Munitionettes’ – and the history of wartime feminism – is secure. Everything about its size, construction, and productivity was of gargantuan proportions. Recalled today as the government’s ‘first sponsored new town in Britain’, Gretna’s output exceeded that of all the other British propellant plants combined. But that was to be only part of the story. At the time, far less was said, and far less made public, about Gretna’s contribution to research and development, to its use of expert management, methods of manpower organisation, and innovation in plant design. Recalling an ‘Oak Ridge’ of a later war, with a safety record that many factories would envy, Gretna’s success held important messages for the future – not least to American observers, who took its lessons home in 1918. This paper will outline some of these characteristics and achievements, and will suggest how those who designed and worked at Gretna succeeded in putting ‘knowledge to war’.