Diplomacy is a 1994 book written by former National Security Advisor and Secretary of State Henry Kissinger. It is a sweep of the history of international relations and the art of diplomacy that largely concentrates on the 20th century and the Western World. Kissinger, as a great believer in the realist school of international relations, focuses strongly upon the concepts of the balance of power in Europe prior to World War I, raison d'État and Realpolitik throughout the ages of diplomatic relations. Kissinger also provides critiques of the counter realist diplomatic tactics of collective security, which was developed in the Charter of the League of Nations, and self-determination, which was also a principle of the League. Kissinger also examines the use of the sphere of influence argument