This book looks at several troop categories based on primary function and analyzes the ratio between these categories to develop a general historical ratio. This ratio is called the Tooth-to-Tail Ratio. McGrath's study finds that this 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 increased, especially with the advent of the large-scale of use of civilian contractors. This work provides a unique analysis of the size and composition of military forces as found in historical patterns. Extensively illustrated with charts, diagrams, and tables. (Originally published by the Combat Studies Institute Press)

This paper clearly shows the immediate relevancy of historical study to current events. One of the most common criticisms of the U.S. plan to invade Iraq in 2003 is that too few troops were used. The argument often fails to satisfy anyone for there is no standard against which to judge. A figure of 20 troops per 1000 of the local population is often mentioned as the standard, but as McGrath shows, that figure was arrived at with some questionable assumptions. By analyzing seven military operations from the last 100 years, he arrives at an average number of military forces per 1000 of the population that have been employed in what would generally be considered successful military campaigns. He also points out a variety of important factors affecting those numbers-from geography to local forces employed to supplement soldiers on the battlefield, to the use of contractors-among others.