The 21st century was the century of the Anno Domini era that spanned from January 1, 2001, to December 31, 2100. During the 21st century, the geopolitical, technological, economic, and social developments of the previous century further matured, leading to continuing innovations within human society and to further challenges. The United States of America, in particular, was affected by these changes. The century began with America as the world's sole superpower, following the end of the Cold War and the dissolution of the Soviet Union. America and its allies grappled with the rise of fundamentalist Islamic terrorism, waging the War on Terror in the Middle East during the first decade of the century.