"While we can only make projections about the characteristics of warfare in 2025, we can say with full confidence that the next war will not be like any the US has fought before. Warfare has changed -- no concrete battle lines exist, technology is an ever-changing friend or foe, and globalization brings myriad players into the equation that did not exist even a decade ago. In order to best prepare the US Army for what lies ahead, we must begin by admitting that we can only predict a fraction of what we will face. Yet, the US Army must prepare and train for these many, and unseen, possibilities. Such preparation requires the use of an adaptable framework that looks not only at the military dimension of an [Operational Environment (OE)] -- but of all the relevant variables. This OE White Paper examines the strategic environment, global drivers, trends and relevant variables to provide a framework to help identify and train for innumerable anticipated strategic, operational, and tactical designs. This document does not state who the next enemy will be, but describes the operational environment of the future to enable the US Army to focus on and train against the capabilities of the next adversary."
Army Deputy Chief of Staff, G-8: http://www.g8.army.mil/