Terrorist groups from around the globe rely on a range of communication tactics to rally support to their political movement, including publicly directed discourse ranging from public talks to online publications. Thus far, the criminological literature has focused primarily on efforts embodied in law and policy to make terrorism harder to commit. Based on the zero-sum assumption that any losses for a terrorist group result in gains for a government, this perspective suggests that terrorism may only be reduced through deterrence or by diminishing the relative capacity of terrorist organizations. In contrast, this dissertation argues that public communications are a relatively inexpensive, readily available, and less oppressive means to potentially reduce terrorism.

Seeking to identify the role that government public communications have played in existing counter-terrorism strategies, this dissertation examines US public communications regarding terrorism delivered by US Presidents and their Press Secretaries between 1970 and 2014. Drawing upon the 6,001 transcripts of presidential communications concerning terrorism during this period, a series of structural equation models are employed to estimate the impact of the quantity and sentiment of presidential communications concerning terrorism on subsequent terrorism aimed at US targets. Findings from these models suggest that the frequency of presidential communications regarding terrorism is consistently related to reductions in terrorism targeting the US in the following month. The frequency of terrorism communications is related to decreases in both domestic and international terrorism, but is also related to increases terrorist casualties between 1970 and 2014. After accounting for the sentiment in these models, support primarily emerged that communicating negative sentiment reduces terrorism in line with restrictive deterrence theory. Key differences in the impact of both the frequency and sentiment of terrorism communications between presidential administrations are also identified, suggesting that influences were more prominent for Presidents such as Carter and George W. Bush. Finally evidence that public approval moderates the impact of presidential communications on domestic terrorism is provided, with presidents with approval ratings in the lowest 25% netting the largest decreases in terrorism but greatest increases in terrorist casualties through their communications.