This book investigates the problem of how United States Department of Defense (DoD) planners should organize the U.S. military, specifically the ground combat elements of the Army and Marine Corps, to meet near-to-midterm security challenges in a fiscally sustainable way. The post-Cold War force structure of the Armed Forces requires more to be spent on defense than two generations ago: yet it is ill-suited to manage the challenges of the twenty-first century strategic environment. In short, the U.S. military has become fiscally unsustainable while the world has become less secure. As such, a drawdown of U.S. military force structure is on the horizon. The question that remains is how to accomplish this drawdown without "hollowing out the military that remains behind. The thesis of this book is that twentieth-century history provides solutions to meet the challenges of the strategic environment while preventing another hollowing out of U.S. conventional combat capabilities. This book examines history to glean lessons learned and provide policy, personnel, training, and material recommendations for current force planners to posture the ground combat elements of the U.S. military to meet its mission requirements during the 2015-2020 time period.