This publication brings together the views of several experts in both the process and substance of defense planning. It argues that an ambitious U.S. national strategy of global leadership will be needed to protect and advance U.S. interests and identifies a range of possible future missions for which we need to prepare. Essays in the volume explore key issues that will arise as the United States fashions its military forces for the coming decades. These include: the roles of military power in U.S. national security strategy; new approaches to planning and evaluating future military force postures; the nature of future military challenges, both in defeating large-scale aggression and meeting smaller-scale threats; which operational capabilities should receive the highest priority; what level of forces future budgets are likely to support; and how the Department of Defense should downsize its infrastructure and reform its management practices. This volume will be of interest to professional defense planners and analysts, as well as students of defense strategy and operations.