Yoram Dinstein's seminal textbook is an essential guide to the legal issues of war and peace, armed attack, self-defence and enforcement measures taken under the aegis of the Security Council. This fourth edition incorporates new material on the wars in Afghanistan and Iraq, response to armed attacks by terrorists, recent resolutions adopted by the Security Council, and the latest pronouncements of the International Court of Justice. In addition, several new sections consider consent by States to the use of force (as expressed either ad hoc or by treaty); an armed attack by non-State actors; the various phases in the Gulf War up to the occupation of Iraq in 2003 and beyond; and immunities from jurisdiction. With many segments rewritten to reflect recent State practice, this book remains a comprehensive and highly readable introduction to the legal issues surrounding war and self-defence. An indispensable tool for students and practitioners.