States generate the hardware of military power by either developing new technologies as first mover or adopting demonstrated technology as second mover. Given that military drones have arguably demonstrated effectiveness and thus proliferate, scholars have produced profound insights into today’s second mover dynamics. Yet, the preceding political process of developing this military technology remains poorly understood. The article’s objective is to explain how states become first movers of military hardware. To this end, it applies four causal mechanisms of military innovation studies to the historical trajectory of the development of drones. I argue that security threats initially formed state interests in drones. Yet, capacity was necessary for success. Politically induced transfers and cross-sector diffusion supplied technological progress. At the same time, distributional implications and legacy systems constrained the development process, but could ultimately be overcome. This mechanismic pathway results from the process-tracing analysis of two separate, but related trajectories in Israel and the United States since the 1970s. Given within-case variation, a sequencing and domain-of-application perspective allows the formulation of scope conditions of the mechanisms behind military innovation. This contributes to a historically contingent, yet generalisable, understanding of the political process of how states generate military power.