The ability to change swiftly from peace, or prolonged low intensity conflict, to the high intensity of war and succeed in the initial engagements is usually discussed in terms of readiness, capabilities, and capacity, and their related materiel, personnel, doctrine, and training. Every security establishment - whether state or non-state - is familiar with these aspects. This book deals with important, complementary, but generally neglected "soft" aspects of moving from peace to war, such as the mental ability to shift from one reality to another; consolidating a coherent doctrine when war erupts in the course of an ongoing peacetime conceptual-doctrinal debate; gaining proficiency on short notice when new weapon systems become available only at the last minute (or even after units have deployed) and so forth. The book draws from historical examples of Israeli “worst case" transition scenarios – namely the Yom Kippur and Second Lebanon Wars, as well as others. Concise examples from American military history demonstrate the endurance and universality of the challenge. Recommendations aimed at enhancing military organizations' preparations for rapidly and successfully transitioning from peace to war complete each chapter and are presented comprehensively in the conclusions.