International Security has once again become a crucial issue in the post-September 11th World. This textbook provides an introduction to both the conventional 'hard' security issues which dominated international relations during the Cold War and the 'soft' security issues which have emerged in the post-Cold War era. Security Studies is traditionally associated with the study of military issues: war and peace, defense, the international arms trade, arms races and arms control, the balance of power and nuclear weapons. In recent years, with the emergence of critical security studies, there has been an increased focus on non-military threats to security such as terrorism, the environment, transnational crime, poverty, economic instability and ethnic rivalries. This textbook is a perfect introduction to both of these aspects of international security in the twenty-first Century.