Military history demonstrates the vital role that geography plays in the planning, execution, and results of any conflict. This project espouses a comprehensive notion of geography that encompasses both physical and human contextual characteristics, as well as relationships that exist between the two. Theorists Carl von Clausewitz and Antoine de Jomini include geography in their discussions on strategy and tactics, and they challenge military leaders to understand its effects when applying combat power. With the importance of understanding comprehensive geography evident in classic theory and the contemporary operating environment, this project examines its contribution to the results of two World War I campaigns in the Middle East. The 1914-16 British campaign against Turkish forces in Mesopotamia found success throughout its first year. However, continued offensive operations toward Baghdad in late 1915 resulted in retreat from Ctesiphon, siege at Kut, failed relief efforts along the Tigris corridor, and the eventual surrender of Kut in April 1916. The evidence suggests that the British leadership's inadequate understanding of the effects of Mesopotamia's human and physical geographies contributed to their operational results. In contrast, Emir Feisal and T.E. Lawrence's understanding of both human and physical geography contributed to their success in the British-sponsored Arab Revolt of 1916-18. These case studies demonstrate that as an element of leadership, an appreciation for all aspects of geography contributed to operational success in the Middle East during WWI by building an understanding of both the physical and human terrain and their effects on military operations. Although recent doctrinal expansion and resource allocation demonstrate the Army's current regard for comprehensive geography, creative changes in personnel and planning processes can further develop its ability to address the complex operating environments of the future.