This monograph examines operational risk in the United States Army and the tendency to subordinate risk because of an institutional focus on aggression, offensive action to seize the initiative, and a reliance on firepower. The tendencies of the American way of warfare compel operational risk acceptance without properly integrating risk into operational planning. U.S. doctrine references risk in many locations, but never really defines it in a useful way or links it to operational purpose and decision-making. The purpose of this monograph is threefold. First, it suggests a model to help planners better understand operational risk. Secondly, it proposes a better definition for operational risk. Lastly, it points out the vulnerabilities the current thinking about risk has caused. This study explores American operational doctrine from 1949 to present to identify the risk tendencies of modern U.S. ground forces and their roots. The monograph examines two case studies of X Corps' advance in Korea during the fall of 1950 to test the tendencies in the doctrine and the risk model. The case studies examine one campaign from two perspectives. The purpose is to examine how two different formations dealt with similar terrain, missions, and risk.