No one - least of all Israel - should be surprised that Operation Cast Lead failed to deter Hamas from firing more than 100 rockets and mortars since the end of the fighting. Deterrence works between sovereign powers whose ultimate interests are served by stability. It works between rivals who have already achieved a relative balance of power that will ensure that each side will not violate the other's sovereign space.

Unilateral deterrence, which reflects the ability of one power to induce an unsatisfied rival to accept the status quo, is an inherently unstable relationship. According to scholar Frank Zagare, if the unsatisfied entity is risk-averse, deterrence may be possible; the more risk-accepting it is, however, the more unrealistic unilateral deterrence becomes. Deterrence doesn't work if one or both of the combatants is a national ethnic group contending for power, because violence is their modus operandi for calling attention to and enlisting support for their cause. Hamas is such a contender, and one that is still holding out for a one-state solution. Let's face it: A two-state solution would never have gained currency in this neck of the woods solely on the strength of college students in North America wearing "Free Palestine" T-shirts.

It is in Hamas' interest to keep the conflict alive and to survive until the tide turns against Israel, which may or may not happen in the foreseeable future. The organization imports and manufactures rockets not so they will serve as a threat, but to use them. Israel may have reduced its enemy's capacity to fire dozens of rockets at a time, but that is only a fleeting victory, which has come at a great political price - the entrenchment of Hamas as the sovereign power in Gaza. That is not deterrence.

Deterrence was no more effective against a Zionist movement intent on establishing a Jewish homeland in the Land of Israel. Indeed, Arab and British violence against the pre-state community, the Yishuv, not only failed to deter the Zionists, but spurred them to further armament. The 1920 riots propelled the Yishuv to develop Ze'ev Jabotinsky's newly formed Haganah; the 1929 riots led to the creation of the Irgun underground; the 1936 riots convinced David Ben-Gurion of the need to produce and import illegal arms. Even as the official Yishuv showed restraint during the tense period after World War II, the more extreme Etzel and Lehi violently maintained pressure on the British. Even when the United Kingdom conditioned entry of 100,000 displaced persons into Palestine on the dismantling of these groups by Ben-Gurion, he demurred.

The period between 1949 and 1967 was the only time deterrence has worked in this ongoing conflict when it involved Israel and the frontline Arab states. The deterrence was particularly effective from 1957-67, after Israel withdrew from Gaza and Sinai, and during which time Egyptian president Gamal Abdel Nasser and Jordan's King Hussein were busy thwarting Syrian and Palestinian efforts to stir things up in the region. It worked because Nasser and Hussein were far more interested in preserving their own regimes than in destroying Israel, and so they were willing to keep their respective borders quiet. Even Baathist Syria, which supported Fatah, forbade Yasser Arafat's organization from launching strikes directly from its territory.

The Six-Day War upset the balance of the previous decade, during which Israel suffered fewer fatalities from terrorism than it did before or has since. Not only did its conquests in 1967 fail to deter Egypt and Syria - which rearmed within months and eventually waged the War of Attrition and the Yom Kippur War - but Israel also released an ethno-national demon. The Palestinian national movement, suppressed by Egypt and Jordan until 1967, was revived by the Six-Day War, and since then Israel has never found a way to effectively prevent it from engaging in violence and terror.

Israel has failed to pursue a decisive strategy in the current round of violence vis-a-vis Hamas. Its choices since 2005 have been, and remain: toppling Hamas; pursuing a cooperative strategy by meeting Hamas' demands concerning the opening of borders; or alternating restraint and diplomacy with retaliation and occasional ground and/or air operations. The first option requires international support, which would only be forthcoming after Israel has genuinely tried the second option. Had Israel eliminated all traces of turning Gaza into an "open-air prison" prior to Cast Lead, and the rockets were still being fired, it might have had a chance to garner the support needed to go all the way in Gaza.

Instead, Israel chose the third path, the one of least resistance, but ultimately a muddled one. That path led to an ill-timed, limited war, which has left Hamas more convinced than ever that it can survive Israel's worst blows. The operation damaged Israel's international reputation, hampering its ability to respond to new provocations from the Gaza Strip with even a mini-Cast Lead operation. Instead of a new reality, we're left to another round of slow boiling, as Hamas turns up the heat at will.

Benjamin Netanyahu may want to unseat Hamas, but one would hope that he knows this option is not politically feasible in the foreseeable future, thanks to Cast Lead. Pursuing a cooperative strategy - accommodating Hamas so as to bring about a cessation of the rocket fire, while remaining aware that it will rebuild its arsenal - is anathema to the prime minister-designate. That leaves door number three.

So, forget about deterrence. It's time to reinforce more buildings in the south.

Steven Klein is an editor at Haaretz English Edition.