The term was first applied post World War II to the British Empire, the United States and the Soviet Union. However, after the end of World War II and the Suez Crisis in 1956, the United Kingdom's status as a superpower was greatly diminished, leaving just the United States and Soviet Union as superpowers. For the duration of the Cold War the United States and the Soviet Union came to be generally regarded as the two remaining superpowers, dominating world affairs. At the end of the Cold War and the dissolution of the Soviet Union in 1991, only the United States appeared to fulfill the criteria of being a world superpower.
Alice Lyman Miller defines a superpower as "a country that has the capacity to project dominating power and influence anywhere in the world, and sometimes, in more than one region of the globe at a time, and so may plausibly attain the status of global hegemony."
No agreed definition of what is a 'superpower' exists, and may differ between sources. However, a fundamental characteristic that is consistent with all definitions of a superpower is a nation or state that has mastered the seven dimensions of state power: geography, population, economy, resources, military, diplomacy and national identity.
The term was first used to describe nations with greater than great power status as early as 1944, but only gained its specific meaning with regard to the United States, the United Kingdom and its empire and the Soviet Union after World War II. This was because the United Kingdom, the United States and the Soviet Union had proved themselves to be capable of casting great influence in global politics and military dominance. The term in its current political meaning was coined by Dutch-American geostrategist Nicholas Spykman in a series of lectures in 1943 about the potential shape of a new post-war world order. This formed the foundation for the book The Geography of the Peace, which referred primarily to the unmatched maritime global supremacy of the British Empire and United States as essential for peace and prosperity in the world.
A year later, in 1944, William T. R. Fox, an American foreign policy professor, elaborated on the concept in the book The Superpowers: The United States, Britain and the Soviet Union — Their Responsibility for Peace, which spoke of the global reach of a super-empowered nation. Fox used the word Superpower to identify a new category of power able to occupy the highest status in a world in which, as the war then raging demonstrated, states could challenge and fight each other on a global scale. According to him, there were (at that moment) three states that were superpowers: the United Kingdom, the United States, and the Soviet Union. The British Empire was the most extensive empire in world history and considered the foremost great power, holding sway over 25% of the world's population and controlling about 25% of the Earth's total land area, while the United States and the Soviet Union grew in power before and during World War II.