World War I or the First World War, often abbreviated as WWI or WW1, began on 28 July 1914 and ended on 11 November 1918. Referred to by contemporaries as the "Great War", its belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fighting also expanding into the Middle East, Africa, and parts of Asia. One of the deadliest conflicts in history, an estimated 9 million people were killed in combat, while over 5 million civilians died from military occupation, bombardment, hunger, and disease. Peace and conflict studies is an academic field which identifies and analyses violent and nonviolent behaviours, as well as the structural mechanisms attending violent and non-violent social conflicts. This is to better understand the processes leading to a more desirable human condition. One variation, Peace studies (irenology), is an interdisciplinary effort aiming at the prevention, de-escalation, and solution of conflicts. This contrasts with war studies (polemology), directed at the efficient attainment of victory in conflicts. Disciplines involved may include political science, geography, economics, psychology, sociology, international relations, history, anthropology, religious studies, and gender studies, as well as a variety of other disciplines. Pacifism may be based on moral principles (a deontological view) or pragmatism (a consequentialist view). Principled pacifism holds that all forms of violent behavior are inappropriate responses to conflict, and are morally wrong. Pragmatic pacifism holds that the costs of war and inter-personal violence are so substantial that better ways of resolving disputes must be found.