Israel’s attack on Gaza rests on an assumption that it can suppress Hamas and thereby remove an obstacle to a negotiated deal with the Palestinians. That assumption in turn requires the conflict to remain limited.

Already, however, there have been demonstrations in other countries protesting Israel’s actions. In Jordan, 88 members of the lower house of parliament voted for a resolution calling for the expulsion of Israel’s ambassador if Israel did not lift its blockade; 22 deputies requested the annulment of Jordan’s peace treaty with Israel. Demonstrators burned the Israeli flag, and thousands of university students marched in support of the Palestinians.

Similarly, thousands of people demonstrated in Egypt, which also has a peace treaty with Israel. Egypt is coming in for special criticism because the Israeli foreign minister, Tzipi Livni, visited just before the assault, leading to accusations that Egypt gave Israel a green light. In addition, Egypt borders Gaza and is therefore in a position t o provide assistance.

The critical nature of Jordan and Egypt was highlighted by Iranian Supreme Leader Ayatollah Ali Khamenei. “Today the heart of the Egyptian, Jordanian and the people of other Islamic countries is overwhelmed with sorrow,” he said in a statement released December 28. “Now, I ask the scholars and Alims of the Arab world and the chiefs of the Egyptian al-Azhar center ‘isn’t it the time to feel the threat facing Islam and Muslims?’ ” By phrasing the issue in this way, Mr. Khamenei is trying to broaden the conflict, taking advantage of popular sentiment. He is reaching over the heads of the governments, appealing to respected religious authorities and to the peoples themselves, and he is redefining the conflict: It is not Israel v. Hamas; it is an assault on “Islam and Muslims.” That is not merely the talk of resistance, it is instigation to revolution.

Indeed, Hezbollah’s leader Hassan Nasrallah has acknowledged the significance of such rhetoric. “I’m not calling for a coup d’etat,” he said on December 28, addressing the Egyptian people (and their army), “but go talk to your leaders and tell them you do not accept what is happening in Gaza.” Can such an appeal work?

Much is made of the difference between Sunni and Shiite, but the question is whether pictures of Gaza in flames will allow Iran to overcome these differences and help forge a new identity based on confronting Israel and its allies. “Nasrallah, who is also a powerful Shia symbol, now enjoys the admiration and respect of the vast majority of the Arab world’s public opinion, which ironically is largely Sunni,” Egypt’s Al Ahram reported after Hezbollah’s 2006 war with Israel. Regarding Egypt specifically, a senior Arab official advised: “Don’t underestimate the significance of Hizbullah flags and posters of Nasrallah in an Arab capital like Cairo.” The situation now recalls the famous metaphor about nationalism: It is like a twig that bends until suddenly, and unpredictably, it snaps back.

Much is made of the passiveness of the Arab street, which has yet to erupt despite years of intifada. Is the twig ready to snap? That seems to be the bet Tehran is making, and those who would dismiss it should recall that the Iranian revolution itself caught most Western experts off-guard. Indeed, that is the nature of revolutions. Those who would dispute that should study our own revolution and see how quickly a movement to redress grievances was transformed into a war for independence, which ultimately gained foreign allies. The British never saw it coming.

Perhaps a military incursion was unavoidable, given the sustained rocket attacks. Certainly, Israelis cannot be expected to submit to assaults without responding. The first obligation of any government is the protection of its people and territory.

If the conflict remains limited, Israel may achieve its objectives. But Tehran has another plan. This war will be decided not in Gaza, but in places like Amman and Cairo.

Wars are easy to start, but they sometimes take unexpected turns. A century ago, changing ideas of identity transformed wars, expanding them and making them more intense and bloody. Are we now about to repeat that tragic experience? The Israelis have rolled the dice, but will Iran win the wager?