From the moment Israel launched Operation Cast Lead against Hamas, one of the most persistently asked questions has concerned its exit strategy: When and how will Israel end this operation?

David Grossman's idea of a 48-hour unilateral cease-fire ("Stop. Hold Your Fire," Haaretz, December 30, 2008) would be a step in the right direction, but it does not address the inevitable scenario of "What next?" - that is, in the event Hamas doesn't stop its rocket fire. A unilateral cease-fire finds currency in conflict-management literature, but it is only valuable if it can be used as a springboard toward reducing long-term violence.

One of the most famous cases of combatants cooperating across enemy lines involved French and German forces in the trenches during World War I. In numerous places along the front lines, soldiers developed codes of behavior by which, for example, each side fired at specified times and targets to minimize casualties on the other side. If that code was violated, the other side would respond with a greater yet defined amount of force.

Robert Axelrod, an American political science professor best known for his work on the evolution of cooperation, developed a theory explaining why sworn enemies would willingly reduce casualties on the other side. Using game theory, he looked at what happens when two sides, each with its own interests, are given the opportunity either to work together toward achieving limited mutual gains, or to lie about their intentions with the prospect of gaining more at the other's expense.

He found that when facing a finite number of encounters, each party - not knowing what the other side would do - inevitably preferred to cheat the other. When both sides cheat, both suffer, yet in repeated studies, this phenomenon - known as the "prisoner's dilemma" - plays itself out to the bitter end.

However, when the sides don't know when the encounters will end, they begin to realize their situation won't improve if they don't cooperate with each other. At that point, they signal to one another their willingness to accommodate the other, and agree to clear rules for responding to violations.

Holding fire and then reciprocating violence with violence, or peace with peace, is a strategy known as "tit-for-tat." It represents cooperation between the two sides rather than submission of one to the other's will.

The strategy being used by Israel and Hamas during the current confrontation is to wage a war of attrition. This creates a zero-sum game, in which each side keeps attacking lest it come out the loser in this round of the conflict. The problem is, Israel doesn't know when Hamas will run out of ammunition and sue for a truce, while Hamas doesn't know when Israel will bow to political pressure and accept an inferior cease-fire, thus allowing the rocket threat to continue.

Tit-for-tat offers an exit strategy. In the current situation, Israel should not simply declare a limited cease-fire, but rather an unlimited one, as well as an end to its blockade of Gaza, contingent on subsequent cooperation by Hamas. Reports indicate Hamas is willing to entertain truce offers - and now is the time for one.

Simultaneously, Israel must communicate clearly to Hamas what the consequences of continued rocket fire would be: For example, for each rocket fired across the border, Israel would close the border crossings for a day, or destroy a certain number of targets.

The advantage of this strategy is that it gives both sides the opportunity to de-escalate the violence and to save face. If the rockets do stop, the Israeli government can tell its citizens that it has secured their safety, while Hamas can tell Gazans it forced Israel to back down and achieved more freedom of movement.

If the rockets continue, Israel would be free of the restraint dilemma it has confronted since the dawn of the Oslo era, while Hamas would emerge as the sole party responsible for the continuation of hostilities. Israel would then enjoy more support from its allies for subsequent military operations.

Skeptics may wonder whether a Western-style tit-for-tat strategy would fail to elicit the desired response from Islamists. However, Hamas has already demonstrated rational behavior by alternating its strategies, between restraint and brinkmanship. Even if hudna (truce) and tahadiyeh (calm) are concepts traditionally defined in Islam as periods used by Muslims to consolidate their strength so as to be able to defeat their non-Islamic enemies later - they also reflect rational decisions.

What is important is that the tit-for-tat strategy serves Israel's interest in securing calm for its citizens without its having to reoccupy Gaza at this juncture, so that it can turn its focus toward a political settlement of the conflict.

Ultimately, there is no guarantee that tit-for-tat would bring an end to the rockets, but if nothing else, it will be a game changer, because Hamas will no longer be able to engage in the brinkmanship of a rocket here, a rocket there, as it has since 2001.

Steven Klein is an editor at Haaretz and is currently writing a Ph.D. thesis in the conflict management and negotiation program at Bar-Ilan University.