For most of the life-span of the historical profession, in most parts of the world, historians were committed to methodological nationalism. Like most other social scientists, they assumed that self-identifying nations, organised politically into states, were the primary objects of historical study. Their main task was accordingly to narrate how nation-states emerged, how they developed and how they interacted with each other. Even those whose work consciously crossed the borders of national histories espoused similar assumptions. Diplomatic historians used national archives to reconstruct relations among states. Historians of immigration tracked the arrival and assimilation of new peoples into existing states. And imperial historians studied empires as the outward extensions of national histories even as they generally maintained a strict separation between the histories of (mostly European) metropoles and their (mostly extra-European) colonies. The matter of history accordingly concerned stability not mobility, what was fixed not what was mixed.

Only the most self-critical historians noted the irony that it was thanks to the global circulation of ideas of nationhood and to the transnational reception of linear conceptions of history that ‘evolutionary nationalist historicism’ became ‘the dominant form of historical understanding across much of the world’. Post-colonial theorists were among the first and most acute critics of nationalist narratives but they have not been alone in questioning the primacy of the nation as the consistent container of history. In response to such challenges, historians in all fields have been moving rapidly towards studies variously described as ‘international’, ‘transnational’, ‘comparative’ and ‘global’. Their efforts have not been identical in scope, in subject-matter or in motivation, nor is there any consensus on how the various non-national approaches to history can be distinguished from each other. International historians often take for granted the existence of a society of states but look beyond state boundaries to the various relationships between them, from diplomacy and finance to migration and cultural relations. Transnational historians examine processes, movements and institutions that overflow those boundaries: for example, the environment, organised crime, epidemics, corporations, religions and international bodies such as the United Nations. Comparative historians deal with distinct historical subjects – often, but not always, nationally defined – in conjunction, although not always on the basis of actual historical connection.