A U.S. Army soldier stands guard from atop a tower at maximum security prison Camp Delta at the Guantanamo Naval Base on August 25, 2004 in Cuba.

It is easy to imagine that U.S. counterterrorism policy began as a response to the 9/11 attacks. But, in fact, efforts to stop terrorism have spanned modern American history—though who was designated a terrorist, and how seriously the threats were taken, shifted dramatically over time.

During the Cold War, the terms terrorist and subversive were largely reserved for Soviet-backed insurgents abroad, communist sympathizers at home, and even civil rights leaders campaigning for equality. American presidents viewed terrorism as a tactical threat, a low-impact security challenge that warranted only limited attention. The Soviet Union and its allies posed the greater strategic challenge. It took the collapse of this archrival in 1991 and the catastrophic events of 9/11, a decade later, to fundamentally restructure the United States’ national security priorities. Once considered a criminal act, terrorism is now seen by U.S. policymakers as an existential threat, both at home and abroad.

In this timeline, we examine the vastly different ways in which U.S. administrations have defined and prioritized domestic and foreign terrorist threats. We look at how these policymakers have balanced the national security agenda with civil liberties such as the right to privacy and the right to a fair trial. It is not an exhaustive list of counterterrorism policies and operations; it rather serves to illustrate changing priorities that ultimately led to today’s nearly two-decade-long war on terror.

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