I specialize in modern German and European politics and the comparative study of communism. Over the years, I have drawn on these interests to investigate a variety of political, historical, and legal themes: authoritarianism; the domestic roots of foreign-policy making; the challenges of democratic transition; the politics of retrospective justice; the comparative politics of internet surveillance; the crisis of democracy, and global communism.  My books include East Germany and Detente; Germany Divided: From the Wall to Reunification; Judging the Past in Unified Germany; Transitional Justice and the Rule of Law in New Democracies; and the The Crisis of Modern Times (also in Chinese and Hungarian translation).

My most recent book, Vanguard of the Revolution: The Global Idea of the Communist Party, is based upon perspectives I have gained over three decades of research and teaching about the communist world.  The foundations for these interests were laid when, as a student at the Free University in West Berlin in 1973, I first experienced the existential journey of passing through the Berlin Wall into East Berlin.  My fascination with dictatorial regimes and the people who support them has stayed with me through all of these years.  I am currently writing about an assortment of “Leninist” New Right thinkers in Europe and America who represent an equally significant threat to liberal democracy.

I am proud to have received doctorates honoris causa from two of the universities that opposed and survived these dictatorships, the Ukrainian Catholic University and the Catholic University of Lublin, Poland.