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: -/US DEPARTMENT OF DEFENSE/AFP/Getty Images

Photo: -/US DEPARTMENT OF DEFENSE/AFP/Getty Images

Why Didn’t Iran Use Terrorism?

Why didn’t Iran turn to terrorism in a war that threatened its survival? Explanations may include disrupted networks, fears of retaliation, and strategic restraint—some factors suggest this is not a break from Iran's terrorism past, but a pause.

Commentary by Daniel Byman — April 13, 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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Why Didn’t Iran Use Terrorism?

Why didn’t Iran turn to terrorism in a war that threatened its survival? Explanations may include disrupted networks, fears of retaliation, and strategic restraint—some factors suggest this is not a break from Iran's terrorism past, but a pause.

Commentary by Daniel Byman — April 13, 2026

The Fragile U.S.-Iran Ceasefire: Issues to Watch

A fragile ceasefire masks a far more dangerous reality: Iran’s nuclear ambitions unresolved, Lebanon destabilized, terrorism risks rising, and a shadow war between Israel and Iran poised to reignite at any moment.

Commentary by Daniel Byman — April 8, 2026

Who Is Winning the Iran War?

The United States and Israel are devastating Iran's leadership and inflicting significant damage on Iran's already-weak military. Iran, however, is hitting back, and the biggest long-term costs to the United States are likely to be felt outside the Middle East.

Commentary by Daniel Byman — April 2, 2026

What Is Israel Trying to Accomplish in Lebanon?

Even as Israel and the United States fight in Lebanon, Israel is also in a major war with Hezbollah—a war designed to keep the group weak and off balance.

Commentary by Daniel Byman — March 19, 2026

Why Did Pakistan Announce “Open War” Against the Taliban?

Early in the morning of February 27, Pakistan’s defense minister announced “open war” between Pakistan and the Taliban, a group that Islamabad frequently backed in its 30-year quest to rule Afghanistan.

Critical Questions by Alexander Palmer and Alexander Margolis — February 27, 2026

What Is Next After the Suicide Attack in Pakistan?

This morning, a suicide bomber attacked a Shia mosque in Islamabad, Pakistan. The most likely perpetrator is the Islamic State–Khorasan Province, which operates both in Afghanistan and Pakistan but has a significant interest in mass-casualty international attacks. 

Critical Questions by Alexander Palmer and Alexander Margolis — February 6, 2026

Why Did the United States Conduct Strikes in Nigeria?

Isolated strikes like the ones carried out by the United States are unlikely to significantly reduce the terrorist threat in the region or reverse Nigeria’s growing insecurity.

Critical Questions by Alexander Palmer and Erin Oppel — December 26, 2025

Ideological Trends in U.S. Terrorism

The Warfare, Irregular Threats, and Terrorism Program examines the state of terrorism in the U.S., finding left-wing violence has risen in the last decade but from very low levels and still well below historic levels of violence by right-wing and jihadist actors.

Analysis by Daniel Byman and Riley McCabe — September 26, 2025