The roots of isolationism in the United States can be traced back to the American Revolution. As a young nation, the United States limited its involvement in world affairs, focusing mostly on trade issues. Only when America's vital interests were threatened did the United States react with military force. In the 19th century, it was possible to isolate the country from trouble abroad. The presence of two vast oceans and friendly countries to the north and south protected the United States from invasion. As the United States grew to superpower status after World War II, however, its interests expanded around the world, as did the allies and resources it had to protect. Although the ideal of a self-sufficient country remains, very few political leaders believe in isolationism, as this new title explains.