The United States has deployed its largest concentration of warships to the Middle East in decades. American forces are engaged in an active air campaign against Iran, facing retaliatory strikes from Iranian-backed militias across Iraq and the Gulf, while sustaining counterterrorism operations in Somalia. The operational questions — where Americans are most at risk, and from whom — dominate the daily threat picture. But a prior question deserves more attention than it has received: What drives insurgent groups with primarily local agendas to target Americans, and what do they gain from it? The new book, Killing Americans: Insurgent Motivations, Risk Factors, and Implications (Oxford University Press, 2026), by Christopher Linebarger, Amira Jadoon, Suzanne Weedon Levy, and Victor Asal, offers answers, drawn from a decade of empirical data on 140 insurgent organizations, that challenge several core assumptions shaping U.S. counterterrorism strategy.

Drawing on a multi-method design that combines statistical analysis of 140 insurgent organizations with four in-depth case studies (the Revolutionary Armed Forces of Colombia, the Tehrik-i-Taliban Pakistan, Al-Shabaab, and the Islamic Movement of Uzbekistan), the book offers a comprehensive framework for understanding both the causes and consequences of anti-American insurgent violence. 

The book's central contribution is twofold. First, it provides a theoretically grounded taxonomy of motivations. Direct factors provide clear incentives for anti-American attacks — religious ideology, U.S. troop presence, and U.S. military aid to insurgent adversaries. Indirect factors create an environment conducive to such attacks or underpin a group's capacity to undertake them — organizational alliances, rivalries, and broader economic relationships. Second, the book demonstrates that anti-American violence yields measurable strategic returns for insurgent organizations, enhancing both their lethality and their survival prospects — a finding with significant implications for counterterrorism policy.

Direct factors provide clear incentives for anti-American attacks, often related to the ideological foundations of insurgent groups or the overt involvement of the United States in their home countries. The book identifies several empirically significant drivers. U.S. troop presence in a conflict-afflicted country is associated with a significantly higher probability that local insurgent groups will target American citizens. U.S. military aid to the government opposing the insurgency is another strong predictor, as insurgents perceive such assistance as the United States directly supporting their adversary. Religious ideology, particularly Salafi-Jihadist frameworks, provides both a moral rationale and operational mandate for targeting Americans. Notably, the study finds that the only insurgent groups to successfully carry out attacks on Americans outside their home state were those motivated by religious ideology.

Indirect motivations refer to cases in which insurgents attack Americans not because of specific American actions, but because of the organizational benefits such attacks confer. In competitive insurgent environments featuring multiple rival groups, attacking Americans can function as an outbidding strategy—signaling operational capability to potential recruits and sympathizers and differentiating one group from its competitors. Alliance networks and inter-group rivalries both amplify this dynamic.

Conversely, the book identifies a mitigating factor: American soft power, operationalized through trade relationships and the presence of American cultural markers, is associated with a reduced likelihood of anti-American attacks. The authors argue that economic interdependence and cultural familiarity may dampen both insurgent motivation and local tolerance for anti-American violence.

Perhaps the book’s most consequential finding concerns what happens to insurgent groups after they attack Americans. The data analysis demonstrates that insurgent organizations that target Americans exhibit increased lethality in subsequent operations and greater organizational longevity. Throughout the entire study period and across the 140 organizations analyzed, only one organization—Indonesia’s Free Aceh Movement (GAM)—ceased operations after engaging in anti-American attacks.

The proposed mechanism is that successfully striking at a superpower signals operational sophistication to multiple audiences simultaneously. Such attacks attract recruits, draw resources from sympathizers, and solidify alliances. Anti-American violence, in this framing, functions as a strategic investment that yields tangible organizational returns. This finding complicates conventional deterrence logic, which assumes that the threat of American retaliation would dissuade insurgent groups from such targeting. The evidence suggests that for many organizations, the reputational and material benefits of attacking Americans outweigh the associated risks.

The book's empirical findings yield several direct implications for U.S. foreign policy and counterterrorism strategy, as discussed below.