In the battle against the terrorists in Gaza, the rules of the game are clear to both sides. The rules are probabilistic, and the game is a Middle Eastern version of Russian roulette. A few rockets from Gaza onto southern Israel are enough to send more than 1 million Israelis running for cover and to keep children from going to school. If the rocket attacks result in significant loss of life, the Israeli government will be left with no choice but to undertake a major ground operation in the Gaza Strip.

Both sides still have painful memories of Operation Cast Lead, which took place less than three years ago. The terrorists in Gaza are counting on the Israeli government's hesitation to undertake such an operation again. The decision about doing so will depend on whether the rocket fire causes casualties, which neither side can predict with certainty.

The probabilities that govern this "game" have changed with the introduction of the Iron Dome batteries that shield some of the cities in the south. It has become more difficult for the terrorists to cause substantial harm to life and limb in Israel, and the likelihood of a major Israeli ground operation in response to rocket attacks has therefore decreased. But in order to decrease the risk of casualties, ordinary life for 1 million Israelis in the south must be suspended when the first rockets hit, and remain suspended until the residents are assured that further rocket attacks are not expected. This uneasy equilibrium between Israel and the terrorists in Gaza cannot last forever.

The root cause of this situation is the large quantity of rockets that have been amassed in Gaza, a stockpile of weapons that is continually expanding. The number of rockets and their range keeps increasing as time goes on, and more and more Israeli cities are coming into range of these rockets. This means that the more time passes, the more the terrorist threat to Israel's civilian population grows.

This dangerous process began with the disengagement from the Gush Katif settlement bloc in December 2005. Successive Israeli governments, refusing to look reality in the eye, did not muster the courage to halt this process in its infancy. The threat will continue to grow until the weapons held by the terrorists in the Gaza Strip are destroyed and the resupply is blocked. This should have been done during Operation Cast Lead, but the task was not completed then.

Ehud Olmert's government labored under the misapprehension that the operation would serve as a deterrent and that another operation could be launched should deterrence fail - only to learn that repeating such an operation is no simple matter. By now it should be clear that once you start, you had better finish the job.

Israel is the only country in the world that is threatened by terrorists who have established themselves within rocket range of its major population centers, threatening its civilian population. An attack by a few hundred rockets disrupts normal life, and a few thousand rockets lead to a major conflagration. There is no equilibrium point in this confrontation. It is an untenable situation that cannot continue indefinitely.

When deployed, Iron Dome changes the probabilities, but not the underlying situation. The stockpile of rockets will have to be dismantled sooner or later, but deterring terrorists is a tricky business. Many, like Islamic Jihad and the resistance groups in Gaza, cannot be deterred; nothing will stop them. Others, like Hamas and Hezbollah, are to some extent sensitive to pressure from their environment because they have assumed political responsibilities in the areas in which they operate. To evade this pressure, they occasionally use proxies they claim not to be able to control, making deterrence problematic.

Hezbollah, along with its tens of thousands of rockets in Lebanon, poses an even bigger threat to Israel than the one from the south. Hezbollah's rockets have the range to cover all of Israel, and no "active defense" like Iron Dome can provide the necessary protection. But they endanger not just Israel, but Lebanon, which in effect is sitting on a powder keg as long as Hezbollah deploys these rockets all over the country in which it is based.

A strike to neutralize such a large number of rockets would inevitably blow a good part of Lebanon sky-high. That is something the Lebanese government and all friends of Lebanon need to keep in mind. The biggest enemy of Lebanon are right there within its borders: Hezbollah, which claims to be the protector of Lebanon but in fact puts the country's very existence at risk. These terrorists need to be disarmed, and the sooner the better.