The Second World War marks the transition to a new mode of warfare, one in which scientific and technical knowledge transformed the fighting of war. Most historical studies have focused on the outputs of national R&D systems and asked what made them succeed or fail. Instead, this chapter highlights the global character of these developments and their disrespect for the temporal end of the war. It explores national innovation systems as individual experiments within a larger landscape of war-relevant R&D. Second World War research crystallized a societal configuration that had been forming since the second industrial revolution. Knowledge and its bearers were understood as the key agents of change in the new social order. The theorists of knowledge economies were looking at post-1945 America, which meant they were observing that setting where the fullest effects of wartime R&D mobilization carried forward into the post-war order.