This book traces the influence of collective memory in International Relations (IR). It inquires where a country's memory first emerges and how it guides states through time in world politics, and locates the origins of national memory in political strategies within the international environment. The study then turns to the domestic landscape, where among a country's public, it finds memory to be the carrier of national identity over time. From there, however, the analysis reverts to the international here: in the medium term, collective memory begins to channel international state behaviour, whereas, in the long run, it circumvents a country's normative horizons. In this book, collective memory is thus assumed to become manifest in world politics in four varying forms: as a country's political strategy, as its public identity, as underwriting its international state behaviour, and finally, as a source for its national values. All four theorized manifestations of memory are tested in a comparative study of (West) Germany and Austria and the impact their diverse post-war interpretations of the Nazi legacy had on their international policies over time. With the illustrative help of the empirical cases, the book not only explores whether collective memory has an influence on political outcomes but how and why it matters for IR.