Given that, globally, health professionals' involvement in crises—especially complex crises where human action plays a contributing role—has risen to new proportions, emergency preparedness is an increasingly integral capacity of health systems. As the United States has come to see itself as vulnerable to violence, its leaders have begun to reorganize the country's health system around protection from terrorism and other health emergencies, upholding this as an essential element or “indispensable pillar” in their strategy for securing the homeland. Biodefense and emergency preparedness have thus come to capture the energies and expertise of nearly all health professionals and, increasingly, to define the specific ends that organize their work.The author thanks Lisa S. Parker and members of the Duke University–University of North Carolina at Chapel Hill Bioethics Forum for their helpful comments on earlier versions of this essay.