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I have chosen to discuss the impact of Roy Brush’s CHDS thesis on the field.    

I was Roy’s advisor, and Carolyn Halladay was second reader.  He was in cohort 1303/4, and graduated in December 2014.

Roy’s thesis was an outstanding example of how CHDS students are often able to use their thesis project to examine a problem or issue that they work with on a daily basis—but which they might not otherwise have the time or opportunity to think much about.

He was then working for the Department of Homeland Security as the coordinator of the National Terrorism Advisory System (NTAS), which was the successor to the much-maligned color-coded Homeland Security Advisory System (HSAS) that had been put in place after the 9/11 attacks.  The old HSAS system had drawn criticism for generating too many alerts, and for leaving color-coded alerts in place for too long, with the result that many Americans paid little attention.  In response DHS created the NTAS system, which was designed to only send alerts when specific threats were detected.  But because such specific warning is rare, in the years it had been in place, the NTAS system had never issued a public alert, even during what were widely considered to be periods of heightened threat such as following the 2011 raid that killed Osama bin Laden, or the 2013 Boston Marathon bombing.

In his thesis research, Roy studied several different types of warning systems and conducted a careful analysis of the advantages and disadvantages of both the HSAS and NTAS systems.  He made a number of recommendations for improving the NTAS system, including a new type of more flexible warning that could be issued even in the absence of specific, actionable intelligence.

Largely as a result of Roy’s thesis, in December 2015 DHS revised the NTAS system to include a new level of warning: a Bulletin, which is used to alert the public to more general trends and developments about the terror threat.  Since then, Bulletins have been issued on a number of occasions, most recently in May 2021 to provide an assessment of the rising threat from domestic terrorism.

Roy’s thesis helped DHS create a new tool to better communicate threat assessments with the public, and it represents the important work our students are doing at the intersection of homeland security theory and policy.

About the Author

Erik Dahl is an associate professor of national security affairs at the Naval Postgraduate School in Monterey, California, where he is on the faculty of both the National Security Affairs Department and the Center for Homeland Defense and Security. His research focuses on intelligence, terrorism, and international and homeland security, and he is the author of Intelligence and Surprise Attack: Failure and Success from Pearl Harbor to 9/11 and Beyond (Georgetown University Press, October 2013). His work has been published in Political Science Quarterly, Studies in Conflict and Terrorism, Intelligence and National Security, the International Journal of Intelligence and Counterintelligence, Homeland Security Affairs, The Journal of Strategic Studies, Strategic Studies Quarterly, and The Naval War College Review, among others. Before joining the NPS faculty in 2008, Dahl was a pre-doctoral fellow at the Belfer Center for Science and International Affairs at Harvard’s Kennedy School of Government. He received his PhD from The Fletcher School of Tufts University, from which he also received a Master of Arts in Law and Diplomacy. In addition, he holds master’s degrees from the Naval War College and the London School of Economics and received his bachelor’s degree from Harvard. Dahl retired from the U.S. Navy in 2002 after serving twenty-one years as an intelligence officer, and in April 2021 he will complete a three-year term as chair of the Intelligence Studies Section of the International Studies Association. He may be reached at


Copyright © 2021 by the author(s). Homeland Security Affairs is an academic journal available free of charge to individuals and institutions. Because the purpose of this publication is the widest possible dissemination of knowledge, copies of this journal and the articles contained herein may be printed or downloaded and redistributed for personal, research or educational purposes free of charge and without permission. Any commercial use of Homeland Security Affairs or the articles published herein is expressly prohibited without the written consent of the copyright holder. The copyright of all articles published in Homeland Security Affairs rests with the author(s) of the article. Homeland Security Affairs is the online journal of the Naval Postgraduate School Center for Homeland Defense and Security (CHDS).

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