We weren't, President Obama emphasized, going to use force to achieve a strategic goal. Whatever was being planned, it would not tip the balance of power in the Syrian civil war one way or another. "Unbelievably small," as John Kerry put it, or as the president said, "A shot across the bow." It seems the plan was to kill in order to put an exclamation mark on a sentence: "America believes in the international laws of war!" or "You'd better keep your fighting within limits, or else!"
The tradition of just war analysis guards against the troubling idea of killing to send a message or for any other symbolic purpose. The probability of success is an important just war principle; another is proportional use of force. Each requires clarity about the on-the-ground outcomes. The Obama administration's refusal to justify intervention in Syria in terms of actual military goals--spokesmen consistently set aside any notion that planned strikes would commit us to Assad's defeat--means that these principles aren't operative. Probability of success: How would we know if killing a thousand Syrian soldiers succeeded in preserving our credibility? Proportional use of force: How many cruise missiles does it take to send a message?
Reasonable people can disagree about when wars are just, and they often do. The criteria of probability of success and proportionality, as well as other just war principles like last resort and even just cause, require judgment calls. But when we can't even apply just war principles, we have no just war at all.
We're not to wage war for the sake of war, or the sake of national pride or credibility, nor should we do so in order to remind the world that we're still the superpower. The moral purpose of war is to counter aggression, defend justice...