The downside of winning a war is that it makes the next one more alluring. Defeating Serbia in Kosovo paved the way for invading Afghanistan. Our early success there made Iraq look as though it would be a cakewalk. Our 2011 victory in Libya is an invitation to plunge into Syria.

The temptation is easy to understand in this case. Syrian dictator Bashar Assad has been practically daring the international community to bring it on, most recently by presiding over a slaughter of more than 100 people, including entire families shot to death execution-style.