Since the advent of the atomic bomb, the United States has always needed two kinds of enemies. On one level, it has needed a tactical enemy that it can go out and fight in the field in a shooting war. Since 1945, these enemies have been created and appeared as North Korea, North Vietnam, Grenada, El Salvador, Panama, Iraq and now Colombia. On another level, however, the US needs a strategic enemy that will justify outrageous expenditures of capital for strategic weapon systems like ICBMs, Trident submarines and "Star Wars" missile defence systems.