Doing Red Lines Right

Syria and Iran won't be deterred by vague commitments.

The jury is still out on how and when the United States will respond to the Syrian regime’s use of chemical weapons, a move President Barack Obama said last year would cross a “red line.” But regardless of what happens next, one thing is already clear: the red line has failed.

Whether the administration strikes back against Bashar al-Assad’s regime or gets it to hand over its chemical weapons, the line will not have achieved its main purpose: deterring the use of those weapons in the first place. After all, the point of red lines is not to guide policy once they are crossed but rather to discourage adversaries from ever crossing them. Assad either did not think that the United States would actually respond or believed that regardless of the response, it was worth launching weapons on rebel strongholds in the Damascus suburbs.

Now, Washington must ask itself why its deterrent failed and what it can do to prevent such failures in the future—particularly in its attempts to stop Iran from acquiring a nuclear weapon. One of the main arguments marshaled in support of a strike on Syria today is that it would send a message to Tehran that the United States takes its red lines seriously. This may be true, but even more important is fixing the system of red lines that allowed Syria to defy Washington’s deterrence in the first place.

Across the world, the United States has a series of red lines in place to keep others from doing things it doesn’t want them to do. Some are so obvious that they don’t need to be stated: everyone knows that the United States would retaliate against an attack on its homeland or military assets abroad. Others need to be stated but are still fairly clear. Few doubt that Washington would go to war in the event of a full-fledged assault on Japan, South Korea or its NATO allies, both because the commitments are enshrined in treaties and because defending liberal allies is known to be a core interest of the United States.

But Washington also draws red lines meant to cover less patent interests. Like the one communicated to Assad, these are the cases in which establishing a believable deterrent is really tricky. Consider Iran. Obama has called the prospect of a nuclear Iran “unacceptable” and has pledged to use force to stop it if necessary. But the threat to bomb centrifuges if Iran rushed for a weapon is not as self-evidently credible as the threat to, say, fight back against a Russian invasion of Alaska (or Poland, for that matter).

It’s possible, then, to imagine that the Iranians would cross the U.S. red line, under the assumption that the Americans would be too war-weary to enforce it. They would probably be wrong to ignore Washington’s threats—just as Assad likely miscalculated in thinking Washington wouldn’t do anything about his use of chemical weapons. But so long as the room for miscalculation exists, the deterrent is not working as intended.

If the United States wants to convince adversaries to respect its wishes in areas that fall outside of its most vital national interests, it needs to make its threats more credible. Simply having the ability to inflict pain and communicating that ability will not cut it. If the United States has the intention to enforce a red line—and it shouldn’t draw red lines when it doesn’t plan to do anything about their being crossed—then it needs to leave its adversaries with no doubt about that intention.

To do so, Washington ought to consider locking itself into certain responses or artificially elevating the degree to which it cares about the actions it wishes to deter. The game theoretician Thomas Schelling called it the “art of commitment,” and explained it as follows in Arms and Influence:“What we have to do is to get ourselves into a position where we cannot fail to react as we said we would—where we just cannot help it—or where we would be obliged by some overwhelming cost of not reacting in the manner we had declared.”

If an American response to a certain action is truly unavoidable, and adversaries that would take that action know it, they could not possibly conclude that Washington lacked the will to punish them. Making a response automatic is practically difficult and also risky—it was an automatic doomsday machinethat ultimately caused the end of the world in Dr. Strangelove. But there are ways to limit the role of natural human hesitancy in decision making, giving opponents less reason to doubt your resolve. For example, the United States can devolve decisions down the chain of command, directly to military forces, giving them the authority in advance to respond to the crossing of a red line.

At the very least, if a deterrent is to be credible, the action it entails cannot depend on approval, in the moment of truth, by a notoriously polarized Congress, whose actions are the very opposite of automatic. A president cannot issue plausible red lines if he has no guarantee of being able to carry out the threat he has in mind.