Karl Marx introduced the concept of historical materialism into the study of world-historical development. In his conception, the economic conditions and dominant modes of production determined the structure of society at that point. Previous historians had focused on the cyclical events of the rise and decline of rulers and nations. Process of nationalization of history, as part of national revivals in the 19th century, resulted with separation of "one's own" history from common universal history by such way of perceiving, understanding and treating the past that constructed history as history of a nation. A new discipline, sociology, emerged in the late 19th century and analyzed and compared these perspectives on a larger scale.