Chapter 3 proposes to define prisoners of war as forced migrants. Although the notions of circulation and imprisonment seem antithetical, this chapter posits that spatial displacements were at the heart of the experience of war imprisonment. It is often forgotten that prisoners of war, by definition, moved, and that this mobility was systemic. For anyone captured at sea, phases of detention on land alternated with internment on anchored or moving ships. The circulations of prisoners of war within, between, and across empires are all part of the same system. By comparing metropolitan, Atlantic, and Caribbean mobility, the shared features of the eighteenth-century state, at home and in the colonies, are highlighted. The prisoners’ strategies to play the system are, it is argued, a side-effect of the limitations of the reach of the state.