Yglesias laments that many politicos still haven't learned it:

I’m strongly inclined to believe that political actors are much too eager to believe that the aggressive use of military force will accomplish their objectives, and also inclined to believe that political actors are much too eager to believe that bloodshed is morally justifiable.

Being chastened is not something Washington ever does well.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.