For two generations, Lebanon remains Israel's mythological ex - that beautiful, worldly and rich neighbor with whom relations once grew from cold to cordial and then from warm to intimate, only to ultimately collapse amid much recrimination, loss and trauma. Israel's Lebanese illusions go back to the late 1950s, when David Ben-Gurion concluded that the Jewish state must court all those in the broader Middle East who don't naturally fall in the Arab-Muslim fold. Consequently, Israel nurtured ties with Christian Ethiopia and non-Arab Iran and Turkey, and sought relations with a long belt of minorities, stretching from the non-Arab Berbers in North Africa and the Christian Copts in Egypt to the non-Arab Kurds in Iraq and the non-Muslim Druse in Syria. While some of this vision was far-fetched, warm relations indeed emerged in those years with the Shah's Iran, Haile Selassie's Ethiopia, and Iraq's Kurdish rebels. During the Six Day War this strategy, which is known as the Periphery Doctrine, nearly resulted in the attack on the Golan extending into Jebel Druse in southeast Syria, where some - led by Labor's Yigal Allon - sought to establish an independent Druse state. Still, nowhere has that doctrine been implemented, and destroyed, as in Lebanon. WITH TYPICALLY Middle Eastern unpredictability, even the Camp David Accords with Egypt did not alter Israel's need for new alliances, since the rest of the Arab world persisted in its rejection of Israel, while Iran was lost at the time to Islamism and Ethiopia to communism. That is how we arrived at the Lebanese misadventure of '82. The vision of a Christian-led, democratic and prosperous Lebanese ally at peace with us collapsed thunderously with president-elect Bashir Jemayel's assassination while the hitherto little-noticed Shi'ites began waging a bloody guerrilla war for which neither the IDF nor the public had been prepared. By the time we left in 2000, most of us identified Lebanon with temptation, intrigue, treachery, disillusionment and disaster. The serene country with which thousands of us became acquainted as soldiers, assuming it would welcome us, first as liberators and then as tourists, shoppers and investors, emerged instead as thankless, hopeless and deadly. How, then, do we ensure that the current battles, indispensable though they are, don't pull us back where none of us wants to return? PARADOXICALLY, the more Israel became fed up with Lebanon the better it understood it. Today Israeli intelligence often knows better than many Lebanese who in their hopelessly fragmented country is scheming what against whom and with what means, tactics and prospects. And this familiarity makes us tell anyone willing to listen that at the end of the day this skirmish is not about Arabs and Jews, but about the clash of civilizations which pits a globalized, multicultural and entrepreneurial Beirut against a spiritually medieval and economically stagnant south Lebanon. Faced with this, and in the spirit of the time-honored Periphery Doctrine, Israel might be tempted to seek a leadership role in an international effort to reinvent Lebanon. This must be avoided. THERE WAS a time when the rest of the world could dismiss Lebanon's tale of two civilizations as an internal affair. Not anymore. In today's world, with fundamentalism on the offensive from Bali, Mumbai and Madrid to Beslan, London and Nairobi, the clash in Lebanon between modernism and fundamentalism carries supreme meaning, since Hizbullah gains there will inspire Islamist violence throughout the world. Israel, however, cannot take part in treating this broader dimension of the situation. The Jewish state has learned, the hard way, that it is in no position to change the Middle East, whether through military means as it tried in '82 or through diplomatic means as it tried the following decade in Oslo. It should avoid at all costs returning to meddle in intra-Arab struggles. Certainly, Israel must refuse to be on the receiving end of everyone else's failure to treat Lebanon's schizophrenia. However, seeking arrangements that would disarm Hizbullah and replace it with Lebanese troops and an Israeli-approved multinational force is not the same as shaping a new future for Lebanon itself. That, like the successful expulsion of Syrian troops last year, should be the business of Lebanon's democrats and the world's superpowers. The major powers must treat the broader Lebanese malaise not out of altruism, but out of an understanding that at stake is Lebanon's emergence as Iran's first foreign conquest. That is why the relevant powers, first and foremost America and France, must now eradicate the scourge whereby foreigners hijacked Lebanon's foreign policy and bullied it into military adventurism. Seventeen years after the end of the Cold War there is already sufficient perspective, and ample evidence, that Islamism has replaced Communism as the main threat to the world's stability, security, prosperity and pluralism. Like the original communists, the Islamists have a built-in urge to conquer turf, and like the medieval inquisition they are possessed by a religious triumphalism that defies constructive dialogue and compromise. They must be fought. However, for the rest of the free world to mistake Israel's current struggle for the one that the entire free world must wage on fundamentalism would be absurd. Israel is fighting not to change Lebanon or make of it an ally, but simply to defend its people. Changing Lebanon, like the defense of all other fundamentalist targets worldwide, is the business of those in a position to shape the international system. Hopefully, they realize that at stake is Teheran's arrival in Beirut, and that losing Lebanon to Iran today might emerge as fateful as losing Spain to fascism proved on the eve of World War II.