The urge to maintain military superiority over potential adversaries has long been a driver of technological advancement. This interplay between defense strength and technology, so evident in the nature of America's military power, has for decades prompted U.S. defense planners to engage in technology forecasting. Analysis of emerging technologies was, and is, vital to making wise defense investments. While it is important to assess the needs and challenges of the future, understanding past military technological successes can be equally important to Army S&T investment and management. By studying past technology development for weapons systems, one can see what factors were important for success and apply these lessons to the management of S&T1 for future systems. This is an especially valuable exercise now, because in recent years there has been mounting pressure to transfer much of the execution of technical work away from the military's inhouse S&T laboratories to the private sector. Whatever the merits of such a move, it represents a significant change from past practices. It would be unwise to undertake any fundamental shifts without first understanding just what was successful about the way the Army S&T program has done business in past years. This book draws on a series of studies known as Project Hindsight Revisited conducted by the authors at the National Defense University (NDU) from 2004-2006. The Project Hindsight Revisited studies examined, in three reports, the development of four current weapons systems of the U.S. Army: the Abrams main battle tank,2 the Apache attack helicopter,3 the Stinger anti-aircraft missile,4 and the Javelin anti-tank missile. In exploring how these weapons systems were taken from conceptual design to full scale production, the studies brought to light crucial factors in their successful development. This book will pursue significant implications of the studies' findings. In exploring these findings, we hope to make a contribution to answering a question that is of the utmost importance to the Army leadership: how are S&T resources best used to advance the state-of-the-art capabilities of U.S. Army weapons systems?