Paradoxes of an Interventionist Foreign Policy
In case you hadn't noticed ...
The U.S. has long been a critic of Assad's government in Syria, supporting, at least verbally, the insurgency against him. Military intervention in support of that insurgency seems to have been seriously considered although never actually implemented. Then ISIS, one of the groups fighting Assad, invaded Iraq and seized substantial amounts of territory, raising the possibility of a takeover of the country by Sunni fundamentalists. The U.S. government responded by air attacks against ISIS in Iraq. It now seems to be seriously considering air attacks on ISIS in Syria.
In other words, they are considering military intervention in support of the same government they were, quite recently, considering military intervention against.
Which reminds me of something I wrote more than forty years ago:
The weak point in the argument is its assumption that the interventionist foreign policy will be done well—that your foreign minister is Machiavelli or Metternich. In order for the policy to work, you must correctly figure out which countries are going to be your enemies and which your allies ten years down the road. If you get it wrong, you find yourself unnecessarily blundering into other people's wars, spending your blood and treasure in their fights instead of theirs in yours. You may, to take an example not entirely at random, get into one war as a result of trying to defend China from Japan, spend the next thirty years trying to defend Japan (and Korea, and Vietnam,. ..) from China, then finally discover that the Chinese are your natural allies against the Soviet Union.
(The Machinery of Freedom, Chapter 45)