The United States Army has relied on a variety of doctrinal manuals for urban operations over the past seventy years. During this period, it conducted operations in Manila, Berlin, Tokyo, Seoul, Saigon, and Panama City, among other cities. While U.S. Army keystone doctrine changed many times to reflect new strategic contexts, urban doctrine remained relatively static. In particular, U.S. Army urban doctrine has never addressed effectively the unique requirements and characteristics of operations in large cities (those with a population over 750,000). Analysis of the history of U.S. Army operations in large cities, considered in relation to relevant doctrine and theory, illustrates the longstanding flaws in the U.S. Army's doctrine and mission execution. The analysis herein describes these challenges in detail, and provides recommendations for updating doctrine to address the special properties of all urban environments - particularly large cities.