The attacks in Paris are yet another reminder that we face enemies who cannot be deterred. The certainty of their own death did not deter the Islamist terrorists who killed in the streets of Paris. But the failure of deterrence is not simply a problem at the tip of the enemy’s spear—namely, the megalomaniacal and perverted individual who desires to blow up himself (or herself). It is also not exclusive to the various groups and cells of Islamist persuasion. Other, more traditional rivals, such as Russia and Iran, also appear to be less amenable to being deterred and are poking around their neighborhood despite their own fragility and weaknesses. They are seeking wars, not avoiding them.
In other words, there seems to be a general crumbling of our—that is, the West’s—ability to deter and thereby maintain order. We are surrounded by wars, and war is penetrating deep into our territories.
There are of course many reasons for the deterioration of deterrence and the resulting instability. One reason is the weakening of our reputation and credibility. Europe long ago ceased to present a convincing capacity to stop or punish enemies beyond momentary spikes of anger and disbelief. It has also been incapable and unwilling to fulfill the basic purpose of any polity: the protection of its own borders.
The United States is not far behind. The belief seems to be that maintaining deterrence does not require hard work. President Obama reserves his anger for his opponents inside-the-Beltway but considers the Paris attack a mere “setback” in the somehow inevitable self-destruction of ISIS. He also seeks to partner with a belligerent Putin, as if the cooperation had until now been missing simply because the two men did not have a private conversation on the sidelines of a summit.
But all of these causes of weakened deterrence are only facets of a deeper problem: our outsized faith in deterrence and the corresponding surprise when our enemies fight. At the heart of this misplaced belief is an assumption of the rationality of all strategic actors, a rationality that can occasionally fail but can nevertheless be cultivated through negotiations, understanding, and the inexorable march of history.
Our Western ancestors did not buy this view. They considered deterrence a fragile, often impossible state of affairs.
Take for instance Diodotus, an Athenian skeptic of deterrence. Diodotus was an otherwise unknown man who debated Cleon, the “most violent man” in Athens, in the fifth year of the Peloponnesian War (5th century BC). The setting was a debate concerning the fate of the Mytilenians, a rebellious population from Lesbos that had been finally subdued by the Athenians. The question under consideration was whether to put them to death or not. Arguing in favor was Cleon; against was Diodotus.
Beyond the points pertinent to the specific question, Diodotus warned not to put too much faith in deterrence. He gave five reasons.
First, cities that rebel or in general go to war always think that they can win. “Was there ever city rebelling,” argued Diodotus, “that did not believe that it possessed either in itself or in its alliances resources adequate to the enterprise?” (Thucydides, Peloponnesian War, 3.45.2) There are many reasons why cities consider their victory likely, but the expectation of victory has often little to do with a real assessment of the political conditions or balance of forces. Once the enemy has convinced himself that he has a chance to win, deterrence is over because it has failed to persuade of the impossibility of victory. War may or may not result; not every city that believes it has a chance to win engages in war. But the conditions for violence are in place. Constant vigilance is indispensable, and a strong will to defeat the undeterred enemy necessary.
Second, Diodotus states the obvious but often discounted truth: “all, states and individuals, are prone to err.” (3.45.3) We tend to underestimate the risks or overestimate the benefits or chances of success.
Third, it is human to desire to take risks. “As long as poverty gives men the courage of necessity, or plenty fills them with the ambition which belongs to insolence and pride … so long will the impulse never be wanting to drive men into danger.” (3.45.4) (Or, better, in Thomas Hobbes’s translation: “For poverty will always add boldness to necessity; and wealth, covetousness to pride and contempt.”) Hope and greed—“far stronger than the dangers that are seen”—constantly undermine deterrence.
Fourth, “Fortune, too, powerfully helps the delusion, and by the unexpected aid that she sometimes lends, tempts men to venture with inferior means.” (3.45.6) Even under the best circumstances, there is always an element of luck or chance. Risk, and thus deterrence, is not a mathematical equation that men can compute.
Fifth, contrary to many modern assumptions, it is more difficult to deter polities or groups of people than individuals, for two reasons. One, communities play for bigger prizes: “the stakes played for are the highest, freedom or empire.” Two, “when all are acting together, each man irrationally magnifies his own capacity.” (3.45.6) As tyrannical regimes know well, solitary individuals are easier to control and dominate than families, groups of friends, or tribes. Similarly, it is easier to deter lone men than members of larger groupings.
It is naive therefore to trust in deterrence, Diodotus tells us. “In short, it is impossible to prevent, and only great simplicity can hope to prevent, human nature doing what it has once set its mind upon, by force of law or by any other deterrent force whatsoever.”
But the fact that deterrence fails does not mean that we have to accept perennial insecurity and instability. It only means that, having failed to persuade the enemy of the impossibility of his victory, we have to defeat him.
When deterrence fails, defeat the enemy.