Palestinian activists called it a preview of new tactics to pressure Israel and win world support for statehood: masses of marchers, galvanized by the Arab Spring and brought together by Facebook, descending on borders and military posts — and daring Israeli soldiers to shoot.

It could prove more problematic for Israel than the suicide bombings and other deadly violence of the past — which the Palestinian Authority leadership feels has tainted their cause.

After attempted border breaches from Syria, Lebanon, Jordan and Gaza left 15 Palestinians dead May 15, Israeli officials openly puzzled over how to handle an unfamiliar new phase.

“The Palestinians’ transition from terrorism and suicide bombings to deliberately unarmed mass demonstrations is a transition that will present us with difficult challenges,” said Defense Minister Ehud Barak.

Arab demonstrators hold Palestinian flags on their May 15 approach to the village of Majdal Shams in the Golan Heights. photo/jta/flash90/hamad almakt

The May 15 protests were driven by renewed hopes that Palestinian statehood — at least as an internationally approved idea within specific borders — is approaching after years of paralysis.

“I want a third intifada,” said one of the protesters, Ala Barghouti, a 21-year-old Palestinian accounting student with tissues stuffed in his nostrils to keep out the sting of tear gas. “I hope things do escalate today … We need to get the Palestinian cause back on world radar again.”

Energized by the uprisings sweeping the Arab world, a recent unity deal between Fatah and Hamas, and hopes for international recognition of statehood by the U.N. General Assembly in September, unusually large crowds turned to the streets to mark the day Palestinians call the Nakba, Arabic for “catastrophe” — Israel’s founding on May 15, 1948.

In both Lebanon and Syria, the Nakba events were meticulously organized. Palestinian organizers bused hundreds to Lebanon’s border with Israel and to the Syrian frontier in the Golan Heights.

Surprised and overwhelmed, Israeli troops fired to keep the crowds from breaching the borders. Four Palestinians were killed in the Golan and 10 in Lebanon, while a 15th was fatally shot as dozens rushed Israel’s border wall with the Gaza Strip.

Many others were arrested, including a U.S. citizen, the State Department confirmed May 17. “Privacy constraints preclude us from providing additional information about this individual’s case at this time,” a State Department statement said.

“The whole Arab world is roiling around the Nakba,” said Professor Eyal Zisser, an expert on Syria at Tel Aviv University’s Moshe Dayan Center for Middle East and African Studies. “Add to that that youngsters think they can make a difference. They decided that instead of just shouting and demonstrating, they’d go across the border.”

The incursion and, more specifically, Israel’s reaction, could not have come at a better time for Syria’s embattled leader, President Bashar Assad. The unrest diverted the world’s gaze from Assad’s growing troubles at home, where military and security forces have responded to anti-government protests by opening fire on demonstrators, shelling neighborhoods and arresting thousands of people in a sweeping campaign of intimidation and torture. More than 850 people have been killed in just two months.

But it also plays directly into the narrative Assad is spinning to maintain his grip on power. Facing an unprecedented threat to his rule, he is desperate to show that only he can guarantee security in a troubled region where failed states abound. The violence along the border was a not-so-subtle message that a calm border with Israel will be the first casualty if Assad is swept from power.

In what Israelis claimed was a Syrian strategy, Syrian forces did not intervene as thousands approached the frontier, hoisting Palestinian flags, shouting slogans and throwing rocks and bottles at Israeli forces. Only after hundreds of people burst across the border fence into the Israeli-controlled town of Majdal Shams did Israeli soldiers opened fire.

Washington openly accused Syria of fostering the violence, with White House press secretary Jay Carney saying that “such behavior is unacceptable and does not serve as a distraction” for the Syrian government. Carney also defended Israel’s right to defend itself.

Some in Israel also suspected that allies of Iran, including the Lebanese Hezbollah militia, had a hand in the uprisings.

Ex-Gen. Yossi Peled, who commanded Israeli troops on the Lebanese and Syrian borders, said border breaches will likely be attempted again, despite the heavy casualties and risk — and must be stopped at any cost, regardless of the political fallout, because they pose a direct challenge to Israel’s sovereignty.

Peled said Israel needs to hurriedly “come up with a new method of warfare where Israel will confront unarmed civilians, children and women.”

Alon Liel, a veteran Israeli diplomat, said the momentum is with the Palestinians. “This is a new type of enthusiasm around Palestinian nationalism, tied to the expectations [of U.N. recognition of a Palestinian state] in September,” he said.

Palestinians say the May 15 uprising was purely their initiative — not the Syrians’ or Iranians’ — launched on Facebook several months ago, with heavy involvement by expatriates. “No one expected it to work, and it did work,” said Hazem Abu Hilal, a Palestinian organizer.

A day after the incidents, Israel filed a complaint with the United Nations Security Council against Syria and Lebanon over the breach of its border by protesters, calling it a violation of international law.

Israeli Prime Minister Benjamin Netanyahu reacted to the uprisings by questioning the Palestinian commitment to peace. “Those that want to destroy us are not partners in peace,” he said.

“I want to make peace with a Palestinian state that wants to end the conflict. I am not willing to accept a Palestinian state that wants to continue it,” he said.  “A Palestinian government, of which half declares daily that it is intent on annihilating Israel, is not a partner for peace.”

Dina Kraft and Uriel Hellman of JTA and additional Associated Press reporters contributed to this report.