The Tetrarchy, or Big 4, refers to the new world order dominated by the West (United States and European Union) and the East (Soviet Union and Southeast Asian Union). It effective replaced the Bipolar World Order during the Cold War. The start of the Tetrarchy era is still disputed, as the United States briefly enjoyed the dominant role in the 1990s after the end of the Cold War and the near collapse of the Soviet Union in 1991. However, the USSR quickly recovered after its successful reorganization into the Union of Soviet Sovereign Republics. A new political, economic and military pact between the USSR and the Southeast Asia Hegemony known as the Eastern Pact and their involvement in the ongoing War on Terror effectively brought both countries into the world stage as superpowers during the 2000s. Meanwhile, the economic boom following the unification of Europe in early 2010s elevated the continent into the rank of superpower.
Other countries with near superpower status include the People's Republic of China (in alliance with the United States despite ideological difference) and India (a neutral country, founder of the non-aligned movement).