This work constitutes a full analysis of Just War Theory in each of its aspects, representing a complete exposition of the corpus of International Law, Jus ad Bellum, and exploring Humanitarian Law of Armed Conflict, Jus in Bello. This comprises the rules that should govern armed conflict, and is called humanitarian precisely because it aims at safeguarding humanitarian values and human rights in times of war. Consequently, this book covers the Law of War in its entirety, both the Jus ad Bellum category - justifications of war - as well as the Jus in Bello category. Extensively analyzed are the following aspects of the use of military force: Self-Defense in International Law, Humanitarian Intervention, National Liberation Wars, Pro-democracy intervention, United Nations Peacekeeping and Peace-enforcement action, Nuclear Weapons, Law of Armed Conflict - International Humanitarian Law, Illegal Use of Force and Statehood.