Israel launched Operation Pillar of Defense last November with the killing of Ahmed Jabari in Gaza City by an armed drone. Jabari, commander of Hamas forces in Gaza, was in a car when the missile hit. Israeli officials called it a perfect operation, based on real-time intelligence and precision munitions. Importantly, no civilians were seriously hurt.

Although the strike eliminated an important Hamas leader, its real value was in demonstrating, again, that Israel can act whenever and wherever it wants to protect vital interests. Which in itself leads to a vital question: How much deterrence does Israel need to dissuade enemies from attacking? It is a question that will soon be answered as government and military officials assess the impact that Operation Pillar of Defense had on eliminating threats posed by the rocket arsenals of Hamas and other militants.

The operation lasted from Nov. 14, 2012, until the 21st, when Egypt brokered a ceasefire. Since Operation Cast Lead in 2008, when Israel sought to end rocket attacks on its cities from Gaza, Hamas and other factions had expanded their arsenals to include longer-range rockets. In 2008, Israeli intelligence believed that all factions in Gaza possessed a total of 5,000 rockets; by the outbreak of Pillar of Defense the total was put at 10,000-12,000, including for the first time rockets that could reach Tel Aviv.

Indeed, those rockets were used during the conflict. The deterrence achieved by Operation Cast Lead afforded Israel some breathing space, which was used to develop the Iron Dome counter-rocket, artillery and mortar system that had a remarkable 85% success rate during Pillar of Defense. This provided security to Israelis living within range of the Gaza barrages. With Iron Dome, Israel demonstrated how technology is a game-changer on the modern battlefield. The system gave decision-makers the freedom to act judiciously. In particular, Iron Dome's success made it unnecessary to launch a costly and politically unpopular ground operation into the crowded and dangerous Gaza Strip.

The primary reason behind the government's decision to embark on Pillar of Defense, however, was its assessment that the deterrence it achieved from Operation Cast Lead had eroded, and as a result Hamas, which controls the Gaza Strip, had loosened its reins on other militants, enabling them to fire rockets at Israel.

Not enough time has passed to make a credible assessment of the operation's results and ramifications in rebuilding deterrence. The minimum goal was viable deterrence—that is, convincing Hamas that launching rockets at Israeli towns could endanger its rule in the Gaza Strip.

A second objective was to destroy the rocket-launching capabilities of Hamas and other organizations, or at least reduce their impact through Iron Dome's interception capability. The use of ground forces for an extensive operation remained an option throughout.

Militarily, Israel emerged from the confrontation with the upper hand. During the operation, it dealt a heavy blow to the rocket systems of Hamas and other organizations, including their infrastructures, launch sites and arsenals—and especially to the Iranian-developed Fajr-5 rocket system, although some of these long-range weapons survived and continued to concern Israel until the ceasefire was reached.

Hamas and other organizations in Gaza have invested years of work in making their rockets more effective. Israel applied the lessons it has learned about conducting asymmetric warfare against terror organizations and paramilitary forces that fire at civilians from civilian areas. The military selected targets carefully, used precision-guided munitions and high-quality, real-time intelligence to minimize civilian casualties and collateral damage.

But Israel cannot ignore the strategic implications that would result from a strike on Iran's nuclear infrastructure, either by the U.S., Israel, or both. The Iranian regime would doubtless uses its proxy Hezbollah in Lebanon to launch massive missile and rocket offensives on major Israeli cities and key military installations. With the capability to launch hundreds of missiles daily from a 60,000-strong arsenal, dozens of Iron Dome batteries would be required. These would take years to produce and adapt to counter such a threat. The David's Sling missile interceptor, estimated to be operational in two years, will add considerable defensive power, but under such conditions, Israel cannot allow itself to be dragged into a war of attrition, where thousands of rockets target its cities, and the government is compelled to launch a large-scale ground and air operation against Hezbollah in Lebanon with devastating results.

Although Israeli analysts believe that Pillar of Defense, along with the 2006 Lebanon war—a 34-day conflict that started when Hezbollah attacked in northern Israel, killing Israeli soldiers—enhanced deterrence, tensions remain high in the area. Israel is monitoring the deteriorating situation in Syria and has expressed its determination to attack and destroy military assets seeping from the Syrian military into Lebanon or to terror groups. Such assets include chemical weapons, coastal- and air-defense systems and ballistic missiles. Israel especially wants to assure that chemical weapons such as sarin, mustard gas and VX nerve agents do not fall into the hands of Hezbollah.

Another strategic imperative is to maintain air superiority over southern Lebanon, where Hezbollah's rocket and missile arsenal is hidden: On Jan. 30, Israeli warplanes attacked a convoy at a military base in Syria that was reportedly transporting advanced SA-17 Grizzly (Buk-M) surface-to-air missiles (SAM) to Hezbollah in Lebanon.

The Israeli air force (IAF) requires full operational freedom over Hezbollah territory in Lebanon. The deployment of weapons such as the SA-17 is unacceptable to Israel, as it was when Syria deployed SA-6 SAMs in 1982: The IAF destroyed them before the First Lebanon War. The SA-17, successor to the SA-6, can hit targets up to 50 km (31 mi.) away and intercept aircraft at altitudes of 10,000-24,000 meters (33,000-79,000 ft.).

The fully mobile system comprises radar and command vehicles, and associated transport and launch vehicles mounting four missiles. Every missile is an independent system, so if one is compromised, the other three remain operational. The individual vehicles are relatively easily camouflaged and later versions have phased-array radar.

Israeli intelligence has established the presence of Hezbollah in Syria, in or near bases holding such weapons, where its crews are being trained in their operation. However, as the Syrian civil war continues, Hezbollah has grown increasingly concerned that its weapons cache could fall into the hands of rebels. The group wants to bring the weapons to its bases in Lebanon, hoping to use weather and camouflage to blind Israeli airborne surveillance.

The Syrian military has also bought the Pantsir-S1 system from Russia, a shorter-range system than the SA-17 but more modern, having only recently entered Russian service. Each self-contained launch unit carries its own radar, 12 ready-to-fire missiles—two-stage weapons designed for rapid acceleration—and two cannon.

According to reports, this was the weapon that downed a Turkish Phantom jet near the Syrian border last summer. Should Hezbollah lay its hands on this system, IAF activity over southern Lebanon and northern Israel would be severely compromised, a situation Jerusalem cannot accept, even if it leads to all-out war.

However, according to senior IAF officers, technological and tactical developments are underway to adapt to the changing situation. Although details remain classified, the Jerusalem Post reported on a lecture held by a senior IAF officer, who claimed that technological upgrades to weapon systems in fighters are creating operational capabilities that would have been seen as borderline fantasy just 15 years ago. The officer was quoted as saying that a single aircraft will be able to strike four targets at long range, with the push of a button. This suggests that fewer sorties will be required to inflict damage with precision ordnance.

What this means is that the IAF is pushing ahead with its strategic assumption that offense, rather than defense (e.g., Iron Dome) will be the decisive factor in future confrontations with Hezbollah, Hamas and other militants and their considerable arsenals of rockets. To avert major civilian and strategic losses, Israel will need to regain its traditional offensive posture—a doctrine of establishing viable deterrence that has safeguarded its security for decades against great odds.