Military ethics is a broadly interdisciplinary study, incorporating concerns about the conduct of war, decisions on how and when to engage in military operations, and issues relating to the moral psychology and care of those who serve and of veterans of military service. It focuses on the core values and moral principles that collectively govern the men and women serving in the military forces of nations around the world, as members of what is sometimes termed the military profession or the profession of arms. The ethical foundations that define the profession of arms have developed over millennia from the shared values and experiences, unique role responsibilities, and reflections of members of the profession on their own practices eventually coming to serve as the basis for various warrior codes and the Law of Armed Conflict (LOAC). Traditional just war theory (political and moral philosophy governing when the use of military force is justified for the resolution of international conflicts) plays a key role in international relations as well as in international law, including the LOAC and international humanitarian law.