The United States government’s declared and orchestrated war on terrorism has internal as well as external dimensions. Externally, it has identified or attempted to identify the terrorist threat with particular nation states, such as Afghanistan and Iraq. But much of the war has been fought internally. Because the enemy could reside anywhere, even within the United States and within those nation states that the United States would never accuse of sponsoring or even condoning terrorism, the war against terrorism requires allies to turn inward to rout out the enemy. For the United States at least, the revision and deployment of immigration law and policy has played an important role in that inward turn.