We learned that the mere invention of a new weapon has almost never affected the course of world events, or altered the balance of power. The real impact of weapons on events comes from the assimilation of weapons into an effective military system. (By assimilation of a weapon we mean its integration into the nation’s milita organization and doctrine in such a way that it is employed effectively and confidently, and that its employment usually results in a relative decrease in the user’s casualties, while permitting the user to inflict higher casualties on military forces that have not assimilated it.) One interesting pattern which emerged from our analysis of assimilation, incidentally, is the fact that it has almost always, through history, taken at least one full generation, or about 20 years, for a weapon to become assimilated after its first adoption. This time lag of about 20 years seems still to be with us today, despite the accelerating trends of technological weapon development. Nuclear weapons, first employed in 1945, have not yet been effectively assimilated into a tactical system by our army or—to the best of our knowledge—any other army—though of course the weapons are available, and can be used. Of the many significant conclusions that emerged from this study, however, one seemed to us to be especially important: New and effective tactical systems in history seem to have been more the result of new ideas than of new or improved weapons. New and imaginative concepts have often permitted inferior forces to overcome handicaps in numbers and/or equipment. We suspect that Vietnam is no exception to this. Another thing which we did in this report was to develop a basis for calculating what we term “lethality indices” for all weapons in history, from hand-to-hand implements of antiquity to nuclear explosives. Using data derived from history, we have been able to calculate the relative theoretical efficiency of weapons, and have discovered that these lethality indices are consistent with actual combat experience in a number of wars which we analyzed in depth. This, in turn, permitted us to develop a quantitative relationship between lethality, mobility, and dispersion in combat. As a military historian, what we did, and what we ended up with, in that study are particularly fascinating to me. I might add that we have also stimulated very gratifying interest in the Army. This very afternoon I presented a briefing of the study report to the Army staff, and discussed some new, and we think potentially important, tactical concepts which the results of the study seem to point out to us. Before leaving the subject of this study, I wish to mention that one of the members of your Society—Mr. Marshall Andrews—was a very important contributor to that study.