During the last decade of the 20th century, the United States became the world's sole superpower. It possessed the world's most productive economy and most mighty military. It dominated global trade and banking, and its popular culture was influential across much of the globe. During the 1990's, the U.S. economy grew rapidly due to a sharp fall in interest rates and the price of oil, the growth of new computer and communication technologies, globalization, and the expansion of international trade, finance, and entertainment. The end of the Cold War unleashed violent ethnic, religious, and national conflicts, especially in the Balkans, the Middle East, and Africa. The first important foreign policy crisis of the post-Cold War era involved Panama, which the United States invaded in 1989 to safeguard American lives and to protect the Canal Zone. This was followed in 1990 by Iraq's invasion and occupation of Kuwait, which was reversed by the Gulf War. The breakup of the former Yugoslavia resulted in U.S. intervention in Bosnia and Kosovo.
Modern warfare is often less a matter of confrontation between professional armies than one of grinding struggles between military and civilians in the same country, or between hostile groups of armed civilians. More and more wars are essentially low-intensity internal conflicts, and they are lasting longer. The days of set-piece battles between professional soldiers facing off in a field far from town are long gone. Today, wars are fought from apartment windows and in the lanes of villages and suburbs, where distinctions between combatant and non-combatant quickly melt away.