Today's U.S. military is full of perplexing questions and issues. Individually, each can be explained, but collectively the explanations seem too complicated. This complexity makes the military difficult to comprehend even to those in uniform. This report is an attempt to understand this complexity and to start a conversation about how to better understand America's 21st-century military. To do that, a return to first principles is necessary, starting with how the nation understands "the common defense" and the role that organized violence plays in providing for it. The nation's understanding of both the common defense and organized violence has changed dramatically in the years since 2001. The diversification in the employment of violence produced a profound paradigm shift that Thomas Kuhn's seminal work, The Structure of Scientific Revolutions, helps to identify and explain. America's senior civilian and military leaders must understand this shift in order to create the military the nation needs in the coming decades and to ensure that it is an institution the American people continue to trust.