Rex 84, short for Readiness Exercise 1984, is a plan by the United States federal government to test their ability to detain large numbers of refugees or American citizens in case of civil unrest or national emergency.
The Rex-84 Alpha Explan (Readiness Exercise 1984, Exercise Plan; otherwise known as a continuity of government plan), indicates that FEMA in association with 34 other federal civil departments and agencies, along with other NATO nations, conducted a civil readiness exercise during April 5-13, 1984. It was conducted in coordination and simultaneously with a Joint Chiefs exercise, Night Train 84, a worldwide military command post exercise (including Continental U.S. Forces or CONUS) based on multi-emergency scenarios operating both abroad and at home. In the combined exercise, Rex-84 Bravo, FEMA and DOD led the other federal agencies and departments, including the Central Intelligence Agency, the Secret Service, the Treasury, the Federal Bureau of Investigation, and the Veterans Administration through a gaming exercise to test military assistance in civil defense.