Combining the English School of International Relations and the study of grand strategy decision-making processes, this article investigates how dynamic density – growing volume, velocity, and diversity of interactions within international society – alters states’ strategy formation processes. By contrasting the perspectives of structural realism and the English School on the role of dynamic density in world politics, the piece illustrates the strategist’s dilemma: as global dynamic density in the international society increases, the ability of great powers to formulate coherent grand strategies and policies potentially decreases. Specifically, it contends that growing global dynamic density generates processual and substantive fragmentation in strategy formation. Building on a large body of elite interviews, US policy toward China – and the so-called US ‘rebalance’ to Asia – is used as a probability probe of the central idea of the strategist’s dilemma. In conclusion, we contrast our findings with complex interdependence theory and examine their implications for ‘great power management’ (GPM) as a primary institution of international society. We argue that, by generating processual and substantive fragmentation in strategy formation, global dynamic density complicates GPM by hindering the capacity of great powers to manage and calibrate the competitive and cooperative dynamics at play in a bilateral relationship.