Stop me if you think that you've heard this one before...

Syria... here we go again.  Apparently the word quagmire has not had enough use in the last decade.  And the US of A is poised to pin on the tin star of world's sheriff once again and go riding to the rescue.  And we probably should, because chemical weapons are nasty and even the war mongers of the 20th century pretty much agreed we shouldn't use them, except for things like Agent Orange, which wasn't technically a weapon because Monsanto said it wasn't, but I digress.
The thing that's so darn frustrating about all this is that we've been on this ride, pretty much constantly, for over 12 years.  It goes like this: there's a bad guy, or group of bad guys, and when I say bad, I mean bad, I don't mean objectively good or even ambivalent, but just bad from an American perspective, I mean bad in the sense that the people who look like them and share their geography and culture also think they're bad: the Taliban/Al Qaeda, Saddam Hussein/ actually not Al Quaeda, and now Bashar Assad / about three dozen rebel groups that may or may not be worse than Al Quaeda.
We've been sort of crossing our fingers and hoping that Syria would play out like Egypt or even Libya, where the people would overthrow their own dictator, but it's not working out.  On top of that Egypt, Libya and especially Iraq have taught us that power vacuums don't always get filled by the good guys, maybe they've even taught us that there really aren't any good guys, or perhaps rather that power, especially the kind of power that is generally associated with the Middle East and North Africa, is rather adept at corrupting people.  Actually, I don't really know what we've learned from the whole mess and I guess that's sort of the problem.
We haven't learned that we can't fix what's wrong in the Middle East with bombs and troops.  There's a whole sub-branch of ethics that deals with something called Just War theory, which accepts the reality that violence is sometimes necessary, but prescribes rather narrow and specific parameters that define when that sometimes is now.  A summary of the rules is as follows (From Biblical Ethics and Social Change, S.C. Mott):
1.The cause must be just.
2. It is the last resort.
3. Force is used by a lawful public authority
4. There is a reasonable hope of victory
5. There is a due proportion between the good that may probably be accomplished and the probable evil effect.
6. The action/war is rightly conducted through the use of right means.

These rules require quite a bit of unpacking and thought to fully wrap your mind around them, however, you don't have to go very deep to see that most of our modern conflicts have violated one, and most often several, of the "rules" of just war theory.  Numbers 5 and 6 are particularly troublesome, as most definitions of "right means" abhor the massive collateral damage that is inevitable in large scale aerial bombing.  Sometimes the definition of "right means" is wrongly brought into conflict with the cost-benefit analysis that is required by number five.  Five is not meant to abnegate the responsibilities of six, it is a different consideration entirely.  "Probable evil effect," is mostly thought of in terms of the casualties of war, in terms of injuries and deaths among combatants and the destruction of property.  The death of a soldier is one thing, the death of an innocent child is another ethical category altogether.  People had started to examine these premises concerning warfare well before the death of women, children and other bystanders became in any sense "inevitable," and it is that inevitability in modern warfare that perhaps gives the final blow to the idea that war can be justified.
Another reality we have not grasped is that, even if our cause is just, even if we fulfill the requirements and act with complete honor and adhere to the codes of battle, the people we have just "rescued" will probably not be in the slightest bit happy to see us.  There is deep anti-American sentiment in that part of the world, largely thanks to the fact that we have been meddling in their business for decades with rather blatant self interest and not always the best or wisest tactics.  We are rather ill suited to play the sheriff in other words, because the townspeople hate us.  It's like when the crooked cattle baron has bought off the law and the sheriff's in his pocket.  Well, it's not too hard to change cattle for oil, and the old west for the Middle East in this little metaphor, and it's not too hard to see that we might very well be a villain, even if we have the right intentions.
Evil works that way sometimes... actually it pretty much works that way all the time.