Mary S. Barton is a historian and analyst based in Washington, D.C. She received her Ph.D. from the University of Virginia in 2016.

Mary S. Barton explores counterterrorism in the years between World War I and World War II, starting with the attempted assassination of French Prime Minister George Clemenceau in 1919, and taking the story up to and beyond the double assassination of King Alexander I of Yugoslavia and French Foreign Minister Jean Louis Barthou in 1934.

In telling the story of counterterrorism over this period, Barton gives particular emphasis to Britain's attempts to quell revolutionary nationalist movements in India and throughout its empire, and to the Great Powers' combined efforts to counter the activities of the Communist International. Further to this, Barton discusses the establishment of the tools and infrastructure of modern intelligence, including the cooperation between the United Kingdom and United States which would evolve into the Five Eyes intelligence alliance. She gives weight to forgotten terrorism and arms traffic conventions, and explores the facilitating role which the Paris Peace Conference and the League of Nations played in this context. The stories told in Counterterrorism Between the Wars play out across the world, from the remains of the Austro-Hungarian, German, and Russian empires, to the Northwest Frontier and the Bengal Province of British India.

A century after the Paris Peace Conference of 1919, Counterterrorism Between the Wars is the first comprehensive study to fit together the mass production of weapons during the Great War with the diplomacy of the interwar era and the rise of state-sponsored terrorism during the 1920s and 1930s.