John McGrath's The Other End of the Spear is a timely historical analysis and an important follow-on work to his earlier analysis of troop density trends in CSI Occasional Paper 16, Boots on the Ground. As that work showed, this paper also shows the timeless value of history and its relevance to current events. Boots on the Ground analyzed the ratio between the numbers of troops employed in military operations relative to the population in a number of irregular conflicts. This study analyzes the composition of such forces to answer the question: what have been the historical trends in the ratio of deployed forces directly engaged in fighting, relative to those engaged in noncombat functions? This ratio is commonly, if inaccurately, called the "tooth-to-tail ratio." McGrath's study finds that the tooth-to-tail ratio, among types of deployed US forces, has steadily declined since World War II, just as the nature of warfare itself has changed. At the same time, the percentage of deployed forces devoted to logistics functions and to base and life support functions have both increased, especially with the advent of the large-scale of use of civilian contractors. A segment of American military historians and policy makers has long been enamored with a genre of military history that seeks to quantify war, to reduce it to known variables, and to posit solutions to future military conflicts based on mathematical formulae. The practice of war contains a strong element of science, but in the end, the practice of war is an art. This study cannot be used to guarantee victory simply by composing a force of the proportional figures presented in the conclusion. However, it does provide a good baseline, based on historical precedent, for future planning. This work, coupled with Boots on the Ground, provides a unique analysis of the size and composition of military forces as found in historical patterns. Policy makers, commanders, and staff officers should use these two studies as a basis from which to begin their analysis of the particular campaign at hand. They will then need to apply their understanding of the objectives, the nature of the conflict, and local and regional culture and conditions to the analysis to create a winning military plan. It is our belief at CSI that this kind of historical analysis will inform and educate today's military and civilian leaders as they carry out our nation's most important policies.