“Sometimes it seems that they only understand the language of force. We have learned from history that the appeasement of an aggressive adversary can be a disastrous mistake, with our concessions only encouraging further attacks on our communities. To deter them from attacking us, we need armed strength, and our leaders must demonstrate the resolve to use it when necessary.” What should we say to someone who describes the Israeli-Palestinian conflict in these terms?

A game theorist is trained to look at conflict problems from both sides, assuming that people on both sides are rational and intelligent. I have tried to write the above quote as one that many Israelis and Palestinians might consider a fair description of their situation, symmetrically identifying themselves as “we” and the other side as “they”, but the symmetry of this view is probably not common knowledge. In particular, many may not understand the other side’s fear of appeasing an aggressive adversary. Such misunderstanding can undermine hopes for peace.

In the above quote, the response to our armed strength that “we” seek from “them” is, in a word, appeasement. We want them to appease us. But why should they not fear that concessions to us could encourage our greater ambitions, inviting further invasion of their communities? And if the demand for armed vigilance on each side is matched by a fear of appeasement on the other side, how can the two sides ever escape from the long war of attrition?

We must think more carefully about the logic of deterrent strategies. Our strategy to deter potential adversaries must have two parts: a threat that we will fight them if they attack us, and a promise that we will be good restrained neighbors if they accommodate us. The difference between our threat and our promise is what encourages them toward accommodation. For our deterrent strategy to be effective, our potential adversaries must understand and believe both the threat and the promise.

Failing to credibly communicate the threat is naive appeasement. Our potential adversaries must not think that we are the weak type of people, who lack resolve to respond forcefully against aggression. To prove that we are not weak may require costly signals of our resolve, many of which have become too familiar: sending out young men on deadly missions against the other side.

But deterrence can fail also if we do not credibly communicate a promise that differs from the threat. If they believe that we are an aggressive type, who cannot restrain ourselves from invading their communities further at any feasible opportunity, then they will feel driven to seek militant leaders against us, and then we will be locked in conflict with them.

How can we demonstrate to them that we are not such an aggressive type? This is a very serious question, because everyone knows that aggressors may try to mask their intentions with honeyed words of peace. The point is not to convince ourselves of our own moral purity; the goal is to convince our adversaries that they can safely make peace with us.

We can effectively signal our restraint by articulating clear strategic limits that verifiably constrain our actions in the conflict, and by showing real understanding and respect for justice as our adversaries see it. Credibly communicating our promise of restraint to a suspicious adversary can be a long and difficult process, but it is an essential part of effective communication in the language of force.

That is the theory. Today we learned that Israel has resisted intense American pressure to freeze expansions of its settlements in the West Bank. It is hard to see this decision as a signal of restraint. Indeed, it seems just the opposite. In rejecting its strongest ally’s interpretation of the legal limits on its expansion, Israel seems to have given a costly signal of an inability to restrain expansionist forces in its political system. Nobody can enter into a treaty without confidence that the other side will accept a mutually agreed interpretation of its limits under the treaty. As a costly signal that reduces the other side’s willingness to make peace, this decision may be less stark than missiles from Gaza, but it is only a matter of degree.