__notoc__ This article refers to the discipline within the field of international relations. For the study of security management see security management studies. Security Studies originated from strategic studies which advanced rapidly during the Cold War and is traditionally held to be an academic sub-field of the wider discipline of international relations. At its core, security studies, as an area of inquiry, takes organized violence as its focus, and the steps individuals and aggregations of individuals can take to both employ organized violence effectively and, much more importantly, to protect themselves from organized violence (accumulation of knowledge in the former being essential for the accumulation of knowledge in the latter). Thus subjects can range from the micro—weapons types, effectiveness, tactics, human-weapons interfaces, individual and group motivations—to the macro; including the causes of war, nuclear strategy, military doctrine, defense spending, and conventional and unconventional strategy. In recent decades however, the security studies field has come under sustained pressure to widen to include areas of inquiry which have not traditionally been the concern of international relations. Traditional approaches to understanding insecurity and security have been taken up by realism, liberalism, and radicalism and their variants. Realism and its variants are held to be closest in spirit to the study of security and strategy because realism holds, at its core, that the global distribution of the threat of war can never be reduced to zero; and because realism and its variants give unit-of-analysis priority to states. Liberalism and Radicalism (and variants) tend to hold out some optimism regarding the eventual withering away of war. A so-called British School, founded for the most part by Hedley Bull, argues that because states are inherently sociable, international politics cannot be reduced to individual states but must focus on aggregations of states much like Samuel Huntington’s later “civilizations” thesis. More recently, however, these traditional approaches to security have been supplemented (one leaves the utility open to argument) by variants such as critical security studies, and the Copenhagen School. Clearly useful contributions to our understanding of insecurity and security have also come from constructivism (international relations), peace studies and critical theory. As implied by the close association of the Cold War with the advent and establishment of security studies as such, broader historical trends (or rather perceptions of them) created the openings that these alternative schools have sought, with mixed effect, to colonize. In particular, WWII marked a watershed in the presumed interest and capacity of states in protecting their own citizens from physical harm. The original principle of sovereignty was an odious bargain whose chief benefit was reducing the likelihood of interstate war and, by extension, the mass killing (or other harm) of people. But after WWII, it became progressively necessary to abridge the principle of sovereignty in order to protect the lives of ordinary people who in previous centuries would have been axiomatically protected—at least from physical harm—as supports to state power. This has led to a great deal of contestation over what “security” means, and whether states remain as useful as foci of interest and explanation as convention would have it. Contemporary security studies is therefore as contested a field of inquiry as it is both interesting and important.