This chapter treats the early modern roots counterrevolutionary war, in Johann Ewald’s (1785) Treatise on Partisan War and (1790) Treatise on the Duties of Light Troops. A Hessian (German) mercenary officer, Ewald served in of one of the earliest and most consequential modern counter-insurrectionary conflicts: the American Revolutionary War. I locate Ewald’s ideas in the intellectual and political context of early modern, absolutist central Europe. He believed in military honor and duty, linked to premodern socio-political hierarchies. In America, he confronted modern ideological warfare, backed by a mobilized populace, for the first time. Gradually, he came to empathize with his opponents and distain the English officers he served. In his diaries, he advocated emulating insurgent tactics—transposing the tools of revolutionary warfare into the military-ideological project of counterrevolution. The two manuals he wrote on returning to Europe alloyed his European and American experiences. They resonated well into the nineteenth century, influencing Clausewitz and informing British conduct of the Peninsular War.