Rex 84B, short for Readiness Exercise 1984 Bravo, was a classified scenario and drill developed by the United States federal government to detain large numbers of United States residents deemed to be "national security threats" in the event that the president declared a National Emergency. The scenario envisioned state defense forces rounding up 500,000 undocumented Central American residents and 4,000 American citizens whom the US Attorney General had designated as "national security threats" as part of the secret Continuity of Government program. These people would be detained at 22 military bases in concentration camps run by the Federal Emergency Management Agency.[1]