Counterterrorism and Homeland Security

Insurgents and violent extremists pose a constantly evolving threat, both in the United States and globally. CSIS research provides strategic thinking on the range of efforts to counter terrorist groups and their methods across the world.

Photo: Keith Birmingham/MediaNews Group/Pasadena Star-News/Getty Images

Photo: Keith Birmingham/MediaNews Group/Pasadena Star-News/Getty Images

Playbook or Rental? U.S. Counter-Drone Defense and the 2026 World Cup

For the 2026 World Cup, the United States built its first nationwide drone defense in months. Whether the country keeps a counter-drone playbook it can carry forward, or returns a six-week rental once the stadiums empty, is the choice it faces the morning after the final.

Commentary by Alexei Hoffman — July 15, 2026

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Seth G. Jones

Seth G. Jones

President, Defense and Security Department; Harold Brown Chair
Daniel Byman

Daniel Byman

Director, Warfare, Irregular Threats, and Terrorism Program
Alek Jovovic

Alek Jovovic

Deputy Director, Center for the Industrial Base and Senior Fellow, Defense and Security Department
Riley McCabe

Riley McCabe

Associate Fellow, Warfare, Irregular Threats, and Terrorism Program

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Playbook or Rental? U.S. Counter-Drone Defense and the 2026 World Cup

For the 2026 World Cup, the United States built its first nationwide drone defense in months. Whether the country keeps a counter-drone playbook it can carry forward, or returns a six-week rental once the stadiums empty, is the choice it faces the morning after the final.

Commentary by Alexei Hoffman — July 15, 2026

Artificial Intelligence and the Future of Terrorism

AI will not transform terrorism overnight. Its more likely effect is subtler: lowering barriers for extremist propaganda, recruitment, disinformation, and planning while strengthening counterterrorism tools and surveillance risks.

Brief by Daniel Byman and V.S. Subrahmanian — July 10, 2026

The War May Be Ending. What Did Epic Fury Cost?

Iran war costs are estimated to be between $34 billion and $42 billion. As neither the FY 2026 defense budget nor the FY 2027 budget request includes war costs, Congress faces a major battle over paying for the war.

Report by Mark F. Cancian and Chris H. Park — June 23, 2026

The Terrorist Threat to the 2026 World Cup

The 2026 World Cup will be the largest sporting event ever held and a magnet for terrorists of all stripes. A new CSIS brief examines who might attack, what targets are at greatest risk, and the countermeasures being deployed.

Brief by Daniel Byman and Riley McCabe — May 27, 2026

Global Terrorism Threat Assessment 2026

Terrorism is currently declining as a U.S. national security priority, and resources available for counterterrorism are decreasing accordingly. At the same time, uncertainty regarding the future of global terrorism is increasing, bringing greater risk of surprise.

Report by CSIS Scholars — May 26, 2026

The Many Faces of Antisemitic Terrorism in the United States

Anti-Jewish violence in America is no longer driven by one ideology alone. Neo-Nazis, jihadists, anti-Israel extremists, and even state-backed actors are converging on the same targets, stretching counterterrorism defenses and redefining domestic security threats.

Commentary by Daniel Byman — May 26, 2026