Ryan is a historian of twentieth-century United States history, with expertise in military history, grand strategy, foreign policy, and political and cultural history. His work examines how the United States pursued national security objectives both at home and abroad, with particular attention to the expanding role of civilian institutions in twentieth-century American strategy. His first book, The Paramilitary Turn: Cold War Policing and the American Garrison State, will be published by Cornell University Press on December 15, 2026. It tells the story of how and why American law enforcement assumed new national security responsibilities during the Cold War, and how this shift changed the relationship between policing and national security.

Ryan’s current project traces the history of “grit” as an ideal of American military leadership. It explores how the qualities Americans celebrated in successful commanders gradually became part of the U.S. Army’s own understanding of professional leadership and, in turn, what those ideals reveal about the nation itself.

In the classroom, Ryan encourages students to think critically about the world they inhabit. Whether discussing military strategy, foreign policy, Major League Baseball, or the politics of punk rock, he challenges students to approach history with creativity and a sense of curiosity.

• Law Enforcement
• Cultural History