In January and February 1991, Central Command Air Forces (CENTAF) conducted an air-to-ground onslaught against Iraq's Republican Guard. The requirements of this operation conflicted in a number of respects with the US Air Force's extended preparations for conflict on a European battleground. A major case in point involved the low-altitude tactics CENTAF crews had practiced for the previous decade and a half, tactics that were manifestly unsuited for the task that confronted them in Iraq. Colonel Andrews's study, "Airpower against an Army: Challenge and Response in CENTAF's Duel with the Republican Guard," examines how CENTAF adjusted air operations against the Republican Guard to meet the realities of combat. As he makes clear, four factors proved instrumental in facilitating CENTAF's rapid adaptation to the realities of war: 1) air superiority which created a permissive environment for innovative tactics, 2) open-minded attitudes of senior commanders which nurtured the growth of new methods of operation, 3) the faith of senior commanders in highly motivated and well-trained subordinates which permitted - and inspired - lower echelon units to find optimal solutions to complex problem in minimum time, and 4) the high degree of personal initiative - cultivated on training and tactics ranges, in classrooms at Nellis Air Force Base, Nevada, and flight briefing rooms across the USAF - which served as the ultimate sine quo non of the adaptation process. Colonel Andrews's study also serves to powerfully reaffirm the fundamental truth of the old Air Force adage that "flexibility is the key to airpower." As we confront an uncertain international security environment, a fundamental lesson of "Airpower against an Army" is that we must encourage flexibility in peacetime if we are to possess the physical, mental, and organizational agility that will be required to master the unforeseen realities of the next war.