When Losing Territory Makes Terrorism Global: ISIS After the Caliphate

Why This Question Matters

Scholars and policymakers have argued that the Islamic State’s loss of control over the population centers that composed its self-declared “caliphate” led the group to internationalize its violence—carrying out higher-profile attacks abroad, shifting where it struck, and producing greater casualties outside Iraq and Syria. James A. Piazza and Michael J. Soules test that widely held claim with systematic data.

What the Authors Ask

Did the territorial collapse of ISIS’s caliphate prompt the group to increase attacks abroad, change the geographic venues of its attacks, and cause higher casualty counts outside its former strongholds?

How the Study Measures Control and Violence

Piazza and Soules assemble original time-series measures of ISIS control over major population centers in Iraq and Syria and link those measures to the group’s observed patterns of terrorist violence. They then use statistical time-series analysis to examine whether reductions in territorial control are associated with changes in the number, location, and lethality of ISIS attacks abroad.

Key Findings

• Loss of control over major cities is followed by a measurable rise in ISIS attacks carried out beyond Iraq and Syria.
• The geographic footprint of ISIS violence shifts outward after territorial losses, with venues of attacks more frequently located in other countries.
• Attacks abroad become more lethal on average after the caliphate’s decline, producing higher casualty counts outside the former territorial core.

Why It Matters for Security and Scholarship

These results provide empirical support for the argument that territorial defeat can push insurgent-terrorist organizations to externalize violence rather than simply diminish their threat. The findings speak directly to debates about counterinsurgency, counterterrorism, and the downstream international security consequences of dismantling territorially based proto-states.

Policy Takeaway

Efforts to retake territory from groups like ISIS may reduce their governance capacity but can also reshape their operational patterns abroad; anticipating and mitigating the internationalization of violence is therefore crucial for post-conflict stabilization and global counterterrorism planning.