On deterrence

As for today, deterrence sounds like a symbol of the old age, an outdated term prevalent during the Cold War, spoken by those passing leaders like Kennedy and Brezhnev.

Deterrence describes a situation that one state shows enough power to persuade the other state from attacking the state. This term was so popular during the Cold War because it precisely represented the relationship between the U.S. and the Soviets. Both of them possess formidable nuclear armory. They were able to launch second strike, the ability to fight back after first round of nuclear strike, to each other. Because of the fear for nuclear retaliation, both of them dared not to attack the other in the first place. This was how war became "cold".

Such a simple logic may not be simple anymore if we take a closer look. States judge whether they initiate attack based on what they know about the capability of their targets. This means there is an information problem between states. In order to successfully deter enemy, it is not enough to strengthen yourself, you must at the same time let the enemy know how strong you are. But exposing the weapon program or deployment status will simultaneously give the enemy tactical advantage to form an attack plan. Therefore, it is always a complex game for states to calculate the risk of releasing information.

Empirically, it is conceptually difficult to assess deterrence. The question is simple. How do we know if deterrence is successful? How do we know it fails? Success deterrence means nothing happens, but if anything happened, deterrence must have failed. In the end, we usually see deterrence failure and hard to tell the successful cases. Then comes the question how long can you count a deterrence success? A state may deter its enemy for 10 years, 20 years, or never had conflict. If conflict takes place in the 26th year, is deterrence successful? Moreover, if success deterrence is a non-occurred event, how do we identify the attacker? Would you say the U.S. deterred Britain as it deterred the Soviets because both of the dyads did not fight war? When we use the term deterrence in conversation, in news article, and in academic papers, we should notice these problems.

From the attacker's point of view, the failure of deterrence is a situation that the target accepts the demand from the attacker. This is what Thomas Schelling calls "compellence". The attacker wants to compel the target to do something it will otherwise not do. Deterrence becomes important because some states want something from other states. If the attacker compel the target, whether using diplomatic coercion or violent force, to do something it wants. The deterrence fails and the target suffers the cost.

It should be noted that attacker also have to suffer cost when it decides to make coercive demand. For example, the cost of warfare, the effect to international trade, the reputation cost for leaders. This suggests target state can raise the cost of attacker to deter it. For example, France built Magino line to deter German attack. The line was trying to make German attack difficult, if not impossible.

An indirect way to raise the cost of the attacker is to strengthen yourself by inviting a friend to fight for you. This is called extended deterrence. This is a very important concept, and still important even today. A state will help another state to deter their common enemy. In most of the cases, a more power state, the defender, will protect a smaller friend, the protege, from the attack of the attackers. This basically explains part of the relationship between alliance members. States form alliance to counter their common enemy, the stronger state provide security promise to protege so the attacker would not dare to make coercive demand to the protege.

Adding more actor in deterrence scenario makes the game much more interesting. Now the attacker needs to consider what would defender do if it makes demand or launch attack. The commitment problem between defender and protege becomes important. More importantly, the defender and protege must single the attacker their willingness to defend the protege. When the commitment gets weak or the attacker misinterprets the intention of defender, the attacker might initiate attack and leads to its failure. The first Gulf War is a clear example. Saddam Hussein mistakenly believed the U.S. would have stayed out of its way if it invaded Kuwait. He launched attack but the U.S. soon came to rescue. Iraq could not get what it wanted, worse of all, it lost significant amount of military force and was imposed 10 years of economic sanction.

Extended deterrence depends on defender's willingness to fight for the protege. This creates an opportunity for the attacker. The attacker can release a limit amount of threat that is acceptable to the defender. As long as defender believe it is not worth intervening, the attacker can turn a multilateral game into a bilateral game. Without the help from the defender, the protege finds difficult to counter the attacker. Therefore, in an extended deterrence scenario, the attacker can manipulate the information to distort defender's commitment. It makes deterrence easier to fail.

Deterrence is not an outdated subject. States still deter each other to form balance of power even today. Extended deterrence is common. East European counties want to introduce NATO to protect them from Russia, South Korea heavily depends on the U.S. to deter North Korea attack. Taiwan still faces a hostile PRC regime and relies on American's security promise. Iran tries to deter U.S. invasion by its nuclear program. North Cyprus counts on Turkish ally to defend its independence.

It is important to recognize that nuclear terror is only part of the story of deterrence. Although states use nuclear capability to deter their rivals, like Israel against Arabs and India-Pakistan against each other, conventional deterrence still plays important role in international relations. States either strengthen themselves, find a strong defender, or signal its firm intention in order to deter the attacker. For example, recent exchange of fire between Thailand and Cambodia over their border dispute gives us some insight. Two parties almost fought a war in 2008. The dispute continued and negotiation was a stymie. The exchange of fire showed both side had to resolve to fight hard, which sent a costly single and raised their cost to fight for the territory. The conflict deescalated and both side negotiated hard to find peaceful resolution because military action is inadvisable. Until now, deterrence still takes effect in Thai-Cambodia border. The fate of temple Preah Vihear is still undetermined. There are many similar border dispute in the world. We do not see fighting everyday because deterrence is having effect.

Moreover, deterrence does not only apply to warfare. It becomes a useful concept in coercive bargaining. The commitment problem, information problem, and costly signal all become important factors for states to decide whether they want to change status quo or telling other states not to change status quo. The emergence and the cause of interstate conflict cannot ignore the concept of deterrence. As states interact in a more complex contemporary world, there are more interlinked disputes between states. Deterrence, a popular terminology from old time, still help us to understand state behavior today.