This book is designed to teach both law students and military professionals the underlying principles governing the law of war and their appropriate applications in various wartime settings. Those applications include means and methods of warfare, use of precision and fully autonomous weapons, cyberwar, treatment of captured combatants and civilians, and treatment of protected places and property. The book also covers specialized issues such as belligerent occupation, nation building, warfare by international organizations, neutrality, ending wars, and the procedural rules and substantive issues in war crimes trials. A chapter on decision-making in wartime discusses command responsibility and gives the student a necessary taste of the underlying reality of combat. Appendices include four non-U.S. law of war manuals not commonly available in English (including the Russian Federation's), a survey of the law of war in U.S. history, and all or substantial portions of important cited cases. A general course in public international law is not necessary for a student to understand and apply the contents of this book.