A political cartoon from 1919 shows the vigilant, toga-garbed figure of Civilization, armed with shield and sword, ready to do battle with Bolshevism, represented by a wild-eyed, wild-haired terrorist. Civilization has just defeated Militarism, represented by a handcuffed German military officer, in World War I.
Clifford Kennedy Berryman/Washington Evening Star via U.S. Library of Congress
The First Red Scare

The First Red Scare spread through the United States on the heels of a growing domestic labor movement and the 1917 Bolshevik Revolution in Russia. It inflamed American fears of communists, radical leftists, and anarchists, who were believed to have threatening ties abroad.

A crowd gathers following a bomb explosion on Wall Street in New York City, on September 16, 1920. Officials blamed the bombing on anarchists and communists.
New York World-Telegram and Sun via U.S. Library of Congress
Bombings Target U.S. Elites

In 1919, anarchists carried out a series of bombings against politicians, judges, and bankers. One bomb exploded at the home of U.S. Attorney General A. Mitchell Palmer, spurring him to create a special division within the Bureau of Investigation (forerunner to the FBI) to gather information on radical political activities.

Men arrested in the Palmer Raids await deportation hearings on Ellis Island, on January 13, 1920.
Thousands Arrested in the Palmer Raids

During the first week of 1920, the Bureau of Investigation responded to public outcry from the bombings with a series of nighttime raids led by Palmer. Federal agents arrested between six and ten thousand suspected anarchists, communists, and radical leftists in thirty-three U.S. cities. Despite public concern over harmful foreign influences, the vast majority of those arrested in the raids were U.S. citizens, and many were not even Communist party members. Ultimately, less than 10 percent of the detainees were deported.

Black Panther Party members demonstrate outside the New York City courthouse, on April 11, 1969. The quotes above them, by Epicurus and Epictetus, respectively, read, “Only the just man enjoys peace of mind” and “Every place is safe to him who lives with justice.”
David Fenton/Getty Images
Social Unrest at Home

Following a decade of post–World War II prosperity for mainstream white Americans, groups advocating for civil rights reform and other political change sparked a period of turbulence and unrest. Reaction to this social upheaval dominated the counterterrorism agenda of the 1960s, with law enforcement targeting domestic groups, individuals, and ideologies deemed threatening to national security.

American civil rights leader Martin Luther King Jr. addresses crowds during the March on Washington at the Lincoln Memorial in Washington, DC, where he gave his "I Have A Dream" speech, on August 28, 1963.
Central Press via Getty Images
Martin Luther King Jr. Draws FBI Scrutiny

Martin Luther King Jr. cemented his name as a civil rights leader when he delivered the historic “I Have a Dream” speech to a crowd of some two hundred fifty thousand people that included members of civil rights, labor, and religious organizations. FBI Director J. Edgar Hoover considered King to be one of the most pressing security threats of the time. A day after the speech, William Sullivan, a Hoover aide, noted in a memo:

“In the light of King’s powerful demagogic speech ... [w]e must mark him now, if we have not done so before, as the most dangerous Negro of the future in this nation from the standpoint of communism, the Negro, and national security.” Six weeks later, Attorney General Robert F. Kennedy authorized full electronic surveillance of King.

J. Edgar Hoover in the Oval Office at the White House in Washington, DC, on July 24, 1967.
Yoichi R. Okamoto
COINTELPRO Targets Subversives

In response to King and other activists, Hoover directed an aggressive FBI operation targeting radical groups that he considered threatening “to the internal security” of the United States. Agents working on Hoover’s operation, called the Counterintelligence Program (COINTELPRO), maintained files on racial justice groups that conducted bombings and assassinations, such as the Black Panthers and the Black Liberation Army. The program also investigated other violent organizations, including left-wing revolutionary groups such as the Weather Underground and the Symbionese Liberation Army, and Puerto Rican nationalist groups such as the Armed Forces of National Liberation (FALN).

But the FBI targeted peaceful activists and activities too. Hoover vehemently condemned the Black Panther’s Free Breakfast for Children program for providing the political group “with a ready audience composed of highly impressionable youths” and called the breakfast program “potentially the greatest threat to efforts by authorities.” Under Hoover, COINTELPRO greatly exceeded the bounds of intelligence-gathering. In 1968, before King’s assassination, the FBI went so far as to send an anonymous blackmail note to King, which appeared to insinuate that he kill himself.

A view of the damage to the U.S. embassy in Beirut, Lebanon, on April 29, 1983, a few days after a terrorist bombing.
U.S. Army
International Terrorism and the Cold War

Throughout the seventies and eighties, hundreds of U.S. citizens died at the hands of state-sponsored terrorist groups. Yet this emerging danger often took a backseat to the Soviet threat, with multiple administrations believing international terrorism to be an unavoidable product of the Cold War.

The explosion at the Marine Corps building in Beirut, Lebanon, on October 23, 1983, created a large cloud of smoke that was visible from miles away.
U.S. Marine Corps
Beirut Barracks Bombing

U.S. Marine and French paratrooper barracks in the Lebanese capital were attacked by suicide bombers who wanted to expel foreign peacekeeping forces from the country. The Hezbollah-linked attackers drove truckloads of dynamite into the barracks, killing 305 people, mostly U.S. and French military personnel.

President Ronald Reagan and First Lady Nancy Reagan honor the victims of the bombing of the U.S. Embassy in Beirut, Lebanon, at Andrews Air Force Base, on April 23, 1983.
Ronald Reagan Presidential Library
Reagan’s Uneven Follow-Up

President Ronald Reagan promised a muscular response to what was then the deadliest terrorist incident in U.S. history, but he followed up unevenly. The United States pulled out of a planned air assault with France, and the White House did little to support ambitious counterterrorism legislation when it stalled in Congress. Reagan’s response was typical for the Cold War period. The concept of international terrorism was nascent and largely overshadowed by conflict with the Soviet Union. Even as terrorist attacks targeted Americans and drew international attention, U.S. leaders did not make meaningful policy changes.

A U.S. flag flies near the base of the destroyed World Trade Center in New York, on September 11, 2001.
Peter Morgan/Reuters
9/11 and the Aftermath

In the deadliest terrorist incident on record, militants associated with the terrorist group al-Qaeda hijacked four planes and used them as weapons to kill 2,977 people and cause extraordinary destruction. The nineteen hijackers crashed two planes into the World Trade Center in New York City and flew another into the Pentagon in Arlington, Virginia. The fourth plane was heading toward Washington, DC, when passengers overtook the terrorists and crashed the aircraft in Pennsylvania. After 9/11, U.S. counterterrorism strategy changed remarkably. No longer a marginal issue, counterterrorism took center stage in U.S. policy both at home and abroad, prompting two wars, a vast government reorganization, and a series of sweeping security measures.

The 15th Marine Expeditionary Unit in southern Afghanistan, on November 25, 2001, after seizing a Taliban base.
Sgt. Joseph R. Chenelly/U.S. Marine Corps
Congress Passes Authorization for Use of Military Force (AUMF)

Three days after the 9/11 attacks, all but one member of Congress voted for a resolution that, in sixty words, authorized the president to respond militarily to those who had “planned” the 9/11 attacks and “harbored” the attackers. This law provided the legal basis for the invasion of Afghanistan and has been used to justify a host of counterterrorism measures, from wiretapping American citizens without warrants to taking military actions against what President Barack Obama called “associated forces” of al-Qaeda. The “associated forces” classification has been interpreted to include the self-proclaimed Islamic State, a group that did not even exist in 2001. The AUMF’s breadth and longevity make it one of the most significant counterterrorism laws ever passed.

A Navy F-18 Hornet jet takes off from the aircraft carrier USS Carl Vinson in the Arabian Sea, on November 12, 2001. Planes from the ship took part in Operation Enduring Freedom strikes against al-Qaeda and Taliban targets inside Afghanistan.
Jim Hollander/Reuters
Bush’s “War on Terror” and the Invasion of Afghanistan

“Our war on terror begins with al-Qaeda, but it does not end there. It will not end until every terrorist group of global reach has been found, stopped, and defeated.” President George W. Bush intended to galvanize and unite Americans with this declaration of a “war on terror.” However, it was a significant departure in military rhetoric because it described a war that was likely without end and certainly without clear boundaries. This war effort began with the invasion of Afghanistan. There, U.S.-led coalition forces not only retaliated against al-Qaeda but also attacked the Taliban for protecting the terrorist group. In 2013, Obama ended the “war on terror,” saying the United States would no longer be fighting a tactic but rather focusing on a specific network of organizations. The United States and its North Atlantic Treaty Organization (NATO) allies officially ended their combat mission in Afghanistan on December 28, 2014, but maintained a presence of at least several thousand troops. In fact, the Donald J. Trump administration has increased U.S. troop presence, which as of early 2018 numbered about 14,000 troops.

The National Security Agency logo is seen on a computer screen inside the agency's Threat Operations Center in Fort Meade, Maryland, on January 25, 2006.
Jason Reed/Reuters
The USA Patriot Act Expands Counterterrorism Powers

The USA Patriot Act comprehensively increased the government’s powers to prevent and combat terrorism. It affected everything from information-sharing by intelligence agencies to penalties for terrorist-related activity. The bill’s provisions on communications surveillance are particularly controversial. The National Security Agency used the Patriot Act to justify its mass collection of phone call metadata for millions of Americans. The information included the numbers called and the dates, times, and durations of those calls. This controversial mass surveillance practice lasted nine years, until the 2015 USA Freedom Act required intelligence agencies to obtain phone records for counterterrorism investigations only on a case-by-case basis.

Detainees in a holding area at Camp X-Ray in Guantanamo Bay, on January 11, 2002.
Petty Officer 1st Class Shane T. McCoy/U.S. Department of Defense
Bush Opens Guantanamo Bay Detention Facility

The first detainees arrived at the Guantanamo Bay naval station on January 11, 2001. Just months earlier, Bush had signed a military order establishing tribunals for non-U.S. citizens who fight against the United States in its war on terror. The order did not classify accused terrorists as prisoners of war, but instead used the term “unlawful enemy combatants,” a designation without the human rights protections guaranteed under the Geneva conventions. The Bush administration detained hundreds of such unlawful combatants in Guantanamo Bay and carried out controversial “enhanced interrogation techniques” in attempts to pry information from the detainees. The Supreme Court eventually ruled that the detainees were protected by the Geneva conventions; however, many of the prisoners remained in detention. At its peak in 2003, Guantanamo held 684 prisoners. Since then, Bush and Obama transferred most of the prisoners out of the detention complex, but forty-one were still there at the end of Obama’s second term in 2017.

Surrounded by members of Congress, President Bush George W. Bush prepares to sign the Homeland Security Act, creating the Department of Homeland Security, on November 25, 2002.
Win McNamee/Reuters
Congress Creates Department of Homeland Security

Congress established the Department of Homeland Security (DHS) in 2002. It was an expansion of the Office of Homeland Security, which had been created by the White House right after the 9/11 attacks. The formation of this cabinet department completely reorganized and expanded government security and counterterrorism efforts. DHS absorbed twenty-two federal agencies related to immigration, emergency preparedness, cybersecurity, and more. It also federalized airport security, which had previously been handled by private companies, by creating the Transportation Security Administration (TSA).

U.S. Counterterrorism: Evolution Over The Past Century