Ever since the terrorist attacks of Sept. 11, 2001, Americans have faced a set of seemingly unprecedented national security challenges and anxieties. Our society has been consumed with debates about government surveillance programs, overseas counter-terrorism campaigns, border security, and extreme proposals to bar foreign Muslims from America—debates that are all, at bottom, focused on finding the proper balance between keeping people safe versus protecting civil liberties.

This debate is not a new one in American history. Even before the Cold War …