Sun Tzu said:
And so one who does not thoroughly know the harm from employing the military ~
Cannot thoroughly know the advantage from employing the military.
And this book is 2300 years old.
The Denma Translation offers the following commentary:
The use of military force is always destructive, to oneself as well as to the other. The general who ignores this will not know how to use the army to advantage, nor the particular advantage in using an army at all. He must be aware of every way that things can go wrong.
The things that went wrong in Iraq were so obvious. I remember thinking at the beginning of the war, "They must have a solid plan for the follow-up actions, for getting the troops out, for 'winning the peace'. The hazards are so obvious that they wouldn't rush in unless they had a solid plan to deal with them, right?"