This essay charts the emergence of a biopolitical militarism during the "Indian Wars," demonstrating the centrality of colonialism to the forms of conflict we now label "counterinsurgency." Most critical work on counterinsurgency and the biopolitics of warfare focuses on the twentieth and twenty-first centuries. However, if we turn our attention to the violence that accompanied US continental expansion, colonialism emerges as a key site for the development of biopower, which manifested in what I call "euthanasia politics." Euthanasia politics names a specific moment in the history of US colonialism when a growing imperative to manage Native life was combined with an increasingly indiscriminate approach to military violence. To these overlapping forms of state power was added the colonial nostalgia of the "vanishing Indian," the presumption that Native people's extinction was inevitable. The US Army during the nineteenth century was preoccupied with Native people as populations to be manipulated, confined, governed, and in many cases, destroyed. In this essay I chart the emergence of this euthanasia politics through the public debate over what was known as the "Indian Question," and I demonstrate how it manifested in the policies and strategies of the US Army.