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.