Throughout the Cold War, Colombia was one of the largest recipients of U.S. counter-insurgency military aid and training. Counter-insurgency–CI for short–was designed to reorient recipient militaries away from a posture of external defence, toward one of “internal defence” against allegedly Soviet-aligned guerrillas. States that received U.S. CI military aid were told to police their own populations to make sure that “subversion” did not grow. Interestingly, when we examine the manuals used by U.S. military trainers to find out what they mean by subversion, we find some interesting clues as to why so many civilians died at the hands of Latin American “internal security states.”