A superpower is a state that is powerful economically and militarily, that can act influentially over most of the globe, that can influence the behavior of other states and maintain that influence for an extended period of time, and can also take effective action on its own, without needing the consent of other nations. In the post-World War II era there have been two superpowers, the United States, and the Soviet Union. Since the demise of the Soviet Union in 1991, the U.S. is the only state that could be called a superpower. However, even a superpower faces restrictions on what it can do to accomplish its goals. The U.S. felt compelled to assemble an international coalition to fight the Persian Gulf War in 1991, rather than go it alone. This also applied to the war in Afghanistan, in which the U.S. established an international coalition before invading in 2001. The U.S. invasion of Iraq in 2003 was also a multinational effort: 39 nations were part of the U.S.-led coalition. Some of these nations may have felt compelled to join to keep their powerful U.S. ally happy, but generally speaking, now there is no longer a Soviet Union as a common enemy, more nations feel free to pursue their own course, without reference to Washington. And in spite of the fact that the U.S. is the sole standing superpower, the political world is now multipolar rather than bipolar: other powers are on the rise, such as Japan, Germany, China, and India, whose status as economic superpowers gives them an increasing influence in world affairs.