Threats of force are an inherent part of communication between some States. One prominent example is the 2017-2018 crisis in relations between the USA and North Korea, marked by multiple threats issued by both sides. Yet, despite that States seem to use threats of force with unlimited freedom, they are prohibited in international law. This book presents threats of force from the perspective of the practice of States. Thus, the book is based on an examination of multiple cases when States reported threats of force. It describes not only what threats of force are, but also provides information on their status as a legal norm, as well as presenting examples, and the mechanisms that are available for States in case threats occur, as well as their legal consequences. The book will be an invaluable resource for academics and researchers in the areas of International Security Law, Public International Law, Law of Armed Conflict and International Relations.