Read Billmon post on forewarnings we had about the Iraq invasion. The quote he ends with, in particular, hit me squarely:

The [Unified Quest] experience left a few, such as Adm. Bien, believing that the best course of action would have been not intervening at all. "We're developing a force that makes it almost too easy to intervene," says Adm. Bien. "I am concerned about America pounding herself out."

If we have to intervene, then the wisest thing to do might be to hit and run instead of staying around to fix what we destroyed. In other words, don't mix national security with politic, ideology, religion, economy, nor conscience.