Realism and the spirit of 1919: Halford Mackinder, geopolitics and the reality of the League of Nations

Recent analyses of interwar International Relations (IR) have argued that there was no realist–idealist debate, and that there is no evidence of a distinct idealist paradigm. Less work has been done on realism in the interwar period. This article analyses the thought of one particular early 20th-century realist: Halford J. Mackinder. A product of the development of political geography, and a major influence on American strategic studies, Mackinder is best known for his Heartland thesis, which has been interpreted as environmental determinism. Yet, Mackinder’s realism is a complex mix of geopolitical analysis and the influence of ideas on human action. His concepts of organizer and idealist foreign policy ideal types pre-date Carr’s realist–utopian distinction by two decades, while his interpretation of the realities of international politics is at odds with Morgenthau’s realism. A closer analysis of Mackinder’s realism (1) underscores the links between geopolitics and realist strategic studies; (2) demonstrates the diversity of realist approaches in interwar IR; and (3) shows that it was possible to be a realist and also support the League of Nations. There are limits to Mackinder’s usefulness to 21st-century IR, but an understanding of his brand of realism is necessary for a fuller understanding of the development of realism as a 20th-century school of thought.