In 1982, following the massacre of 800 Palestinian civilians in Beirut, about 500,000 Israelis took to the streets.

Although the Palestinians had been killed by a Christian militia and not by Israeli troops, the demonstrators demanded the ouster of Defense Minister Ariel Sharon, who had sent the militiamen into the Sabra and Chatilla refugee camps.

The protesters were also furious about a war that was intended not, as the government originally claimed, to defend northern Israel from Palestinian rockets but to alter the balance of power in Lebanon, a goal they considered optional. As a result of the rally, Sharon was forced to resign.

Twenty-four years later, the Israel Defense Forces are back in Lebanon, occupying swaths of the south and bombing Beirut. Hundreds of Lebanese civilians have been killed -- by Israelis, not by their proxies -- and immense damage caused. Much of the world and the media are as critical of Israel's conduct in this war as they were in the previous one, insisting that the Israeli attacks have been "disproportionate."

Yet, in contrast to 1982, Israelis today are overwhelmingly supporting their army's actions. And apart from expressing regret over the loss of civilian lives, they show no sign of wavering. Israeli flags and banners proclaiming "Be of Strength and Courage!" (a biblical quote) literally line the streets.

Why? What makes this Lebanon war different from the last one?

To begin with, Israelis, too, are under fire this time. During the last few weeks, Hezbollah has shot more than 2,500 rockets and mortars at Israel, killing at least 17 civilians, wounding 500 and forcing more than half a million people to flee. The attacks from Lebanon coincided with aggression from Gaza, where Hamas terrorists fired about 1,000 Kassam rockets at Israeli towns and farms.

The war, Israelis now know, is not about borders but about the existence of the Jewish state.

On both fronts, Israeli soldiers were the victims of unprovoked ambushes and kidnappings. And these attacks have come despite the fact that Israel is no longer occupying any part of either Lebanon or Gaza. The war, Israelis now know, is not about borders but about the existence of the Jewish state.

Israelis also know that Hezbollah cares nothing about civilian casualties on either side. On the contrary, Hezbollah wants Israel to cause the maximum amount of collateral damage among Lebanese in order to expose Israel to international condemnation. That's why Hezbollah missile launchers are routinely deployed in civilian neighborhoods.

As a rule, Israeli forces warn Lebanese civilians to leave the battle areas, but eventually they have no option but to destroy these structures or risk losing more Israeli lives to the rockets fired at them. The Israeli air force must also knock out the roads, runways and bridges that Hezbollah uses to replenish its arsenal.

More pressing than the need to defend Israel's heartland, however, is the need to protect Lebanon from Syria and Iran. Counterintuitive though it sounds, Israelis understand that the only way to save Lebanon is by bombing it.

After languishing for years under Syrian occupation, Lebanon has been hijacked by the Syrian-supplied and Iranian-directed Hezbollah. The Lebanese government and army are powerless to control this force, much less disarm it. Hezbollah's burgeoning power not only permits Syria to continue its occupation of the country but, more perilously, it enables Iran to realize its dream of establishing an unbroken arc of Shiite militancy from the Mediterranean to the Persian Gulf.

An Iranian takeover of Lebanon not only threatens Israel's security but also that of moderate Sunni states throughout the region, and it endangers Europeans and Americans.

In mounting its counteroffensive against Hamas and Hezbollah, Israel is drawing a line in the sand against the Iranian leaders who have sworn to wipe it off the map and who, for that purpose, are developing nuclear power.

Israel's purpose is not retribution but survival.

In 1982, Israel's objective was to install a pro-Israeli government in Beirut. But its goal today is to prevent Lebanon from becoming a fully armed outpost of Iran.

Needed to help accomplish that is a robust international force to secure Lebanon's borders from all foreign encroachments, disarm all illegal militias and establish the sovereignty of the democratically elected government in Beirut.

Sharon, who eventually returned to politics and became the first Israeli prime minister to recognize the Palestinians' right to statehood and to uproot Israeli settlements, now lies in a coma. He leaves behind a legacy of one Lebanon war that most Israelis opposed — but also a sense of sobriety and resolve that has persuaded Israelis to support this Lebanon war and steeled their determination to win.