Today the United States is fighting a "war" against terrorism, a military action whose definition will be a matter of controversy, particularly, if history is any guide, between Congress and the president. Throughout its history, the United States has grappled with the constitutional tension built into the conduct of its foreign affairs and the interpretation of the power to make war and use force abroad. Since the Cold War's end, the United States has had to navigate through a period of strategic ambiguity, where American national security interests are much less certain.