This follows from his statement in Politics Among Nations: "The main signpost that helps political realism to find its way through the landscape of international politics is the concept of interest defined in terms of power, " (Morgenthau). This principle defines the system of sovereign states from the realist point of view. Hans Morgenthau holds that in the anarchic system that is international relations one value above all others explains the actions of states, that value being the pursuit of power. States in the international arena are consumed with maintaining their power as well as the acquisition of new power. In his perspective, the world is dominated by individual countries vying for power at the expense of others, in what can be called a "zero "sum game " of national security. He provided much of his insights during the height of the Cold War, when perhaps this sort of struggle was at its greatest intensity, between the two superpowers of the Soviet Union and the United States. The entire world became a stage, from Asia to Africa, Europe, and the Americas, where both tried to triumph over the other in increasing their influence abroad and their security by creating allies in these regions. For one of the superpowers to triumph in one area was a loss to the other, and although war never came about between the two, proxy wars, coups, and other forms of conflict within foreign countries became the means to outdo the other. If the United States gained an ally, the Soviet Union lost one, and would be less secure in the world, losing influence and being surrounded by enemies.
Realists tend to see other actors in the international arena (non-governmental organizations, the United Nations, treaty organizations, transnational terror groups) as secondary to states and are often simply manipulated by states as they maneuver for power. To the realist, a great game is at play and states will use whatever tools or means to increase their power or influence.
