While World War I certainly represents a historical rupture in Europe and many parts of the world, there are diverging views in scholarly literature and broader historical discourse regarding its character as a dividing line between historical periods. The essay identifies three main positions within the debate and elaborates on the broader consequences of these interpretations. Several scholars consider World War I as the end of an earlier, longer historical era. According to another periodization, the two World Wars and the two decades separating them make up an era together, which is distinct from the pre-1914 and post-1945 periods. Finally, a third major current interprets World War I as the overture to a new epoch. Each of the three approaches can be relevant to research on World War I and the twentieth century, but there are considerable divergences between the interpretations thus produced. If we regard World War I as the endpoint of the previous era, then great emphasis should be placed on the road leading up to the war. If we conceive of the two World Wars and the decades between them as a single unit, then we should focus on violence as a defining feature of the periodization, and short-term factors should be highlighted. Finally, if we understand the Great War as the beginning of a new period which lasted until the end of the twentieth century or beyond, World War I will be seen as the Urkatastrophe (primordial catastrophe) that set the stage for World War II and, indirectly, for the Cold War, while also generating seminal long-term processes in politics, society, and the economy.