Volunteering on both sides of the border, I witnessed how the wall predictably mutilates the bodies of those who try to scale it. The adoption by the Border Patrol of the “prevention through deterrence strategy” in 1994—which involved increasing the length and the height of the border fence in urban areas—significantly expanded the number of wounded migrants. The shifting design of the border fence produces particular forms of injuries: The sharp edges on top of the previous fence, made of corrugated sheet metal left over from the Vietnam War, amputated limbs; the tall, slatted steel wall we have today fractures legs and ankles. In towns along Arizona’s southern fringe, ambulances go to pick up wounded border crossers so frequently that emergency responders refer to the cement ledge abutting the wall as “the ankle alley.” The border wall is a key component of “tactical infrastructure”—a concept that Customs and Border Patrol uses to refer to the assemblage of materials and technologies that regulate movement in the name of national security. It includes gates, roads, bridges, drainage structures and grates, observation zones, boat ramps, and lighting and ancillary-power systems, as well as remote video surveillance, which together “allow CBP to provide persistent impedance, access, and visibility, by making illicit cross-border activities, such as the funneling of illegal immigrants, terrorists, and terrorist weapons into our Nation, more difficult and time-consuming.” Such “tactical infrastructure” simultaneously produces victims and marks them as criminals.