Strategic Interaction In International Relations

The development of the modern state system and the concept of an international system are generally traced to the Peace of Westphalia of 1648, which brought to an end the Thirty Years' War in Europe. Prior to this, while states existed in name, the focus had been on the various monarchs and religious leaders who dominated Europe. The Peace of Westphalia established the principle of sovereignty, which remains a fundamental element controlling international relations today. The establishment of the concept of sovereignty effectively meant that a state's political leadership (initially, mostly monarchs) had ultimate authority within a state's borders and that others had no right to intervene in the internal affairs of another state.

The result was a system that encouraged the establishment of independent nation-states and the institutionalizing of state interaction through the mechanism of diplomacy. The subsequent colonization of the rest of the world by the leading European states meant that this system became global and was finally institutionalized with the formation of the United Nations. The United Nations Charter has been endorsed by virtually all the states of the world; contained within it is guidance on how force may and may not be used and the responsibilities of states to their citizens. This entry discusses the international system, diplomacy, international law, and institutions that support the international system.