The challenges that vex the United States today in Iraq, Afghanistan, and elsewhere are not altogether as new and unique as they seem. U.S. involvement in Central America during the 1980s clearly demonstrated the costs, risks, and limits to intervention and the use of force in internal conflicts. Much can be learned today about the nature of irregular warfare from the experiences of the United States and the other protagonists in Central America during the final phase of the Cold War. The U.S. perceived a threat to national security in these wars from determined insurgents with a...