This isn't an exact quote, but it gets to the point.
If you don't know your enemy or yourself you will loose every war.
If you don't know your enemy but you do know yourself, you'll
win half the wars.
If you know your enemy and yourself you will win every war.
I think that is part of the problem. Pre Vietnam most wars had a battle line. You were here and the enemy was on the other side of the road. You could see him shooting at you and you shot back. It is not like that any more. At least for the GI at the checkpoint. The next guy walking up to your post, down the street toward you, or standing in the line beside you, could be the guy who does not mind being blown to hell and not care who goes with him.
dave
