Questions related to peace, security and defence are increasingly present in the public debate on International Relations, and their growing complexity means that the concepts must be used with the greatest academic rigour. This work stresses this, going successively deeper into each of its four blocks, in a study of war and peace in international society; prevention mechanisms, management and resolution of conflict and international controversies; the developemnt of the concept of security and, finally, investigation of the various meanings of defence. The theoretical exploration of the various concepts gives insight into their historical evolution and their use by various actors. All this with the bibliographical tools and electronic links for each topic aims to open a window into a world in which the reader is encouraged to delve deeper and broaden his knowledge.