Earlier this month, the U.S. ambassador to Syria, Robert Ford, made an extraordinary trip to the besieged city of Hama. His visit was meant to support tens of thousands of peaceful demonstrators holding olive branches and roses in a city ringed by troops.

This was more than a brave diplomatic gesture aimed at discouraging further Syrian crackdowns. It was a recognition of a powerful new strategy of protest that has toppled autocrats in Tunisia and Egypt and may yet oust harsher tyrants. It could even become a crucial factor in the struggle between Israelis and Palestinians.

I refer to nonviolent action used in strategic ways.

We all witnessed the peaceful tactics that undermined autocrats in Tunis and Cairo, where armies refused to fire on unarmed protesters. But experts argue that such tactics won't work against more determined despots as long as their armies hold firm.

Thus, we watched the forces of hard-line ayatollahs crush millions of protesters in Iran's Green Revolution, while civil war drags on in Yemen and Libya. And despite weeks of demonstrations in Syria, President Bashar al-Assad has yet to make meaningful concessions. His officer corps, filled with members of his minority Alawite sect, has so far held firm and has been willing to fire live rounds into unarmed crowds.

Yet developments in Hama, along with the lessons of Egypt's revolution, show how nonviolent resistance could undo Assad.

Assad can't ignore Syrian public sentiment, or wider Arab and international opinion. His economy is vulnerable to sanctions. His largely Sunni (and increasingly religious) population will get video feedback of massacres, even with Internet restrictions.

What Egyptian protesters would tell their Syrian counterparts is: Use nonviolent tactics to exploit these vulnerabilities until the regime cracks.

Syrian opposition groups are probably familiar with the strategy of nonviolence described to me by a prominent Egyptian activist named Dahlia Ziada. Now the Egypt office director of the American Islamic Congress, Ziada translated a comic book about the Rev. Dr. Martin Luther King Jr. into Arabic in 2004 and attended a workshop on nonviolence at Tufts University's Fletcher School in 2008.

In recent years, her organization set up civil resistance training sessions for dozens of Egyptian activists, who in turn spread the message. Many other young Egyptians found their way on the Internet to materials produced by the Washington-based International Center on Nonviolent Conflict. Moreover, the approach of the demonstrators in Tahrir Square was instinctively nonviolent, even among those with no training; there were constant chants of "silmya, silmya," meaning peaceful or no problem.

Of course, in Egypt, unlike in Syria, the military had no history of firing on civilians. But even in Syria, the regime rests on "pillars" that the opposition can weaken with nonviolent tactics. Sunni merchants, scared minorities or soldiers can be wooed more readily by peaceful protesters than by armed rebels.

This doesn't guarantee that nonviolence will succeed, especially in the short run, or that it will frighten determined killers. But if a situation is ripe, nonviolent protest may be the most potent tool of Arab rebellions -- and one that will be used more often by Palestinian protesters now that peace talks with Israel have failed.

So Ambassador Ford was wise to make his risky voyage to Hama. It has become the symbol of Syrian revolution. And it will surely test the power of nonviolent revolt.