Professor Tooley specializes in Modern European History and his books include The Western Front: Battleground and Home Front in the First World War, Ethnic Cleansing in Twentieth-Century Europe (with Steven Bela Vardy), and National Identity and Weimar Germany.

His articles and reviews have appeared in such scholarly journals as History Teaching Review Yearbook, Canadian Review of Studies in Nationalism, The Independent Review, Central European History, Journal of Libertarian Studies, Quarterly Journal of Austrian Economics, American Historical Review, and History: Reviews of New Books.