This book analyzes the concept of likelihood of success in just war thinking and argues that if the concept should be retained, it must be reconsidered within the overall whole of the tradition of just war. The concept of likelihood of success has stood out as particularly troublesome to thinkers and practitioners in the just war tradition. The idea, while related to the other categories of just war, such as proportionality and military necessity, can at times be confused with being an absolute rather than a co-belligerent criterion within the broader just war canon. With such an abstraction, justice can be collapsed into a kind of pragmatic calculation, favoring the powerful, and virtually invalidating insurrection, rebellion, or resistance. This volume brings together scholars and experts from across the tradition to reconsider and reconceptualize the likelihood of success. It analyzes this concept not only in light of the war in Ukraine and the war in Gaza, but also in historical cases such as Thermopylae or the Russo-Finnish Winter War. It also examines how we categorize and calculate the likelihood of success and what, after all, we mean by "success." Further, the volume considers how close or far from the target we should get, or expect to get, before claiming that a war is "unjust" or immoral, and raises the issue of the destructiveness caused by defenders themselves. This book will be of interest to students of just war theory, military ethics, statecraft, and international relations generally.