President George W. Bush recently spoke of lessons to learned from Vietnam; mainly that if the U.S. leaves, chaos will follow. The true lesson is that if the U.S invades without careful thought is that chaos follows. Put more broadly, the lessons which few military thinkers have learned are:
1) Pick your wars carefully
2) Know thine enemy
3) Have sufficient resources to win
4) Change strategy and tactics as needed
5) Know when you have failed and get out
