This historical overview indicates that under the impetus of wartime patriotism and concerns over national security, the American courts and public have generally supported the combined efforts of Federal, State, and local law enforcement in domestic national security operations, even at the temporary expense of civil liberties. This support, however, continued only up to a certain point, and only for a period of time, i.e., until peacetime conditions resumed. Following each wartime domestic crisis, the pendulum of public and judicial favor typically swung back toward restraint on law enforcement and a restoration of the traditional peacetime balance between security and traditional civil liberties. Current administration policies and law enforcement operations related to national security, homeland security, and the War on Terror have been controversial from the outset of legislative deliberations and public response; however, there has been a solid and vocal constituency of support for a strong response to the terrorist threat, to the extent of equating dissent with disloyalty to the national interests in time of war. It remains to be seen whether strong support for current security practices will be sustained when the fear related to September 11 and the threat of a similar terrorist attack diminishes. The historic periods examined in this chapter are World War I and the “great red scare” (1917-1921); World War II, 1939-1945; the early Cold War and Korean War, 1950-1953; and the Vietnam Era, 1965-1975. 19 references