Opening a security conference in Tehran on July 8, Iranian President Mahmoud Ahmadinejad exhorted the Islamic world to mobilize against Israel and "remove the Zionist regime." The nations of the region are growing furious, he said. "It will not be long before this intense fury will lead to a huge explosion."

Four days later, Hezbollah terrorists staged a raid across Israel's northern border, kidnapping two Israeli soldiers and killing eight more. Over the next day, more than 120 rockets rained down across northern Israel. Among the communities struck was Haifa, Israel's third-largest city and home to its busiest port and a large oil refinery. It was the first time rockets fired from Lebanon had penetrated so far into Israel; Haifa had been thought to be out of Hezbollah's range.

Israel replied to Hezbollah's artillery barrages and hostage-taking with a military invasion, much as it did in Gaza last month in response to incessant rocket fire and the Hamas kidnapping of Gilad Shalit. In short order, Israel's warplanes struck Beirut's international airport, Hezbollah's offices, and two Lebanese army bases; the Israeli navy put Lebanon under a blockade.

And so by week's end Israel was at war again, this time on two fronts against two of the most lethal terrorist forces in the world. Except that the real enemy confronting it is not Hamas and Hezbollah. Terrorist organizations cannot function without state sponsorship, and no state anywhere sponsors more Islamist terrorism than Iran.

Was it just a coincidence that Ahmadinejad's prediction of "a huge explosion" came only days before Hezbollah's assault across the border and its unprecedented attack on Haifa? Or did the rabid president of the evil regime that bankrolls Hezbollah with an estimated $200 million a year know what was coming? It was Iran that supplied Hezbollah with its immense arsenal of artillery rockets. When Hezbollah launches them at Israel, it is doing the bidding of its patron.

The same is true of Hamas, which is likewise financed by Iran. The top Hamas mastermind held a press conference in a Damascus ballroom last week, where he extolled the Syrian regime that shelters him. Syria is in turn protected by Iran, with which it signed a military cooperation pact in June. So it came as no surprise when Ahmadinejad warned Israel not to extend its military offensive to Syria, and threatened "a crushing response" if it did.

Israel has to repair its deterrent threat, which was weakened by the unilateral retreats from Gaza and southern Lebanon and by too many listless responses to terrorist provocations. A sustained assault into southern Lebanon, one that leaves Hezbollah in shards and Israel's northern border at peace, would be welcome evidence that the old Israel is back. And it would represent a significant victory in the worldwide war against Islamist terrorism.

Gaza, Hezbollah, Iraq, Al Qaeda: It is all the same fight. "No one should have any lingering doubts about what's going on in the Middle East," writes Michael Ledeen, an expert on terrorism and Iran. "It's war, and it now runs from Gaza into Israel, through Lebanon and thence to Iraq via Syria. There are different instruments, ranging from Hamas in Gaza to Hezbollah in Syria and Lebanon and on to the multifaceted `insurgency' in Iraq. But there is a common prime mover, and that is the Iranian mullahcracy, the revolutionary Islamic fascist state that declared war on us 27 years ago and has yet to be held accountable."

Twenty-seven years ago was 1979, the year that Islamist radicals loyal to the Ayatollah Khomeini invaded the US embassy in Tehran and held dozens of American diplomats hostage for the next 444 days. Washington's response was weak and feckless, as it would be time and again in the years that followed. Only after 9/11 did the United States finally acknowledge that it was in a war with militant Islam and begin fighting back in earnest. But not against Iran, which continues, unscathed and unrepentant, to stoke the terrorist fires. Its goals, unchanged since Khomeini's day, are to become the dominant power in the Middle East, to create Islamist regimes worldwide, to annihilate Israel, and to kill Americans.

We will never win this war, Ledeen and others argue, until the Iranian theocracy is brought down. That does not have to mean military action. Our aim instead should be to empower Iran's restive population, which is largely pro-Western and moderate. Give them as much support as possible, much as the Reagan administration did for Lech Walesa and Solidarity in Poland -- and let them find the means to reclaim their government for themselves.

Israel may be able to inflict a punishing defeat on Hezbollah, but regime change in Tehran will require American resolve. Will we muster that resolve before -- or only after -- the mullahs get the bomb?