In war, there are always differences between the opponents. At times these are insignificant, passing disparities with no bearing on the outcome. At other times, the differences between opponents are important, placing one in a position of advantage, the other at a disadvantage. This is a very simple observation, but from it flows one of the pressing issues faced by the United States today: strategic asymmetry. Strategic asymmetry is the use of some sort of difference to gain an advantage over an adversary. It is an idea as old as warfare itself, appearing under a number of guises. Among strategic theorists, Sun Tzu placed great stock in psychological and informational asymmetry, writing that: All warfare is based on deception. When confronted with an enemy one should offer the enemy a bait to lure him; feign disorder and strike him. When he concentrates, prepare against him; where he is strong. avoid him.