This Nakba Day was unlike the many that have come before. The Palestinian Arab Spring is arriving, and Israel has little defence against it.
On an old anniversary, a new sense that change is possible
They are extraordinary scenes. Film shot on mobile phones captured the moment on Sunday when at least 1,000 Palestinian refugees marched across no-man's land to one of the most heavily protected borders in the world, the one separating Syria from the Israeli-occupied Golan Heights.
Waving Palestinian flags, the marchers braved a minefield, then tore down a series of fences, allowing more than 100 to run into Israeli-controlled territory. As they embraced Druze villagers on the other side, voices could be heard saying: "This is what liberation looks like."
Unlike previous years, this Nakba Day was not simply a commemoration of the catastrophe that befell the Palestinians in 1948, when their homeland was forcibly reinvented as the Jewish state. It briefly reminded Palestinians that, despite their long-enforced dispersion, they still have the potential to forge a common struggle against Israel.
As Israel violently cracked down on Sunday's protests on many fronts - in the West Bank, Gaza, Jerusalem and on the borders with Syria and Lebanon - it looked less like a military superpower and more like the proverbial boy with his finger in the dam.
The Palestinian "Arab Spring" is arriving and Israel has no diplomatic or political strategy to deal with it. Instead on Sunday, Israel used the only weapon in its current arsenal - brute force - against unarmed demonstrators.
Along the northern borders, at least 14 protesters were killed and dozens wounded, both at Majdal al Shams in the Golan and near Maroun al-Ras in Lebanon.
In Gaza, a teenager was shot dead and more than 100 other demonstrators wounded as they massed at crossing points. At Qalandiya, the main checkpoint Israel created to bar West Bank Palestinians from reaching Jerusalem, at least 40 protesters were badly injured. There were clashes in major West Bank towns too.
And inside Israel, the country's Palestinian minority took their own Nakba march for the first time into the heart of Israel, waving Palestinian flags in Jaffa, the once-famous Palestinian city that has been transformed since 1948 into a minor suburb of Tel Aviv.
With characteristic obtuseness, Israel's leaders identified Iranian "fingerprints" on the day's events - as though Palestinians lacked enough grievances of their own to stage protests.
But, in truth, Israeli intelligence has warned for months that mass demonstrations of this kind were inevitable, stoked by the intransigence of Israel's right-wing government in the face of both Washington's renewed interest in creating a Palestinian state and of the Arab Spring's mood of "change is possible".
Following in the footsteps of Egyptian and Tunisian demonstrators, ordinary Palestinians used the new social media to organise and coordinate their defiance - in their case challenging the walls, fences and checkpoints Israel has erected everywhere to separate them. Twitter, not Tehran, was the guiding hand behind these demonstrations.
Although the protests are not yet a third intifada, they hint at what may be coming. Or, as one senior Israeli commander warned, they looked ominously like a "warm-up" for September, when the newly unified Palestinian leadership is threatening to defy Israel and the United States and seek recognition at the United Nations of Palestinian statehood inside the 1967 borders.
Ehud Barak, the Israeli defence minister, alluded to similar concerns when he cautioned: "We are just at the start of this matter and it could be that we'll face far more complex challenges."
There are several lessons, none of them comfortable, for Israel to draw from the weekend's clashes.
The first is that the Arab Spring cannot be dealt with simply by battening down the hatches. The upheavals facing Israel's Arab neighbours mean these regimes no longer have the legitimacy to decide their own Palestinian populations' fates according to narrow self-interest.
Just as the post-Mubarak government in Egypt is now easing rather than enforcing the blockade on Gaza, the Syrian regime's precarious position makes it far less able or willing to restrain, let alone shoot at, Palestinian demonstrators massing on Israel's borders.
The second is that Palestinians have absorbed the meaning of the recent reconciliation between Hamas and Fatah. In establishing a unity government, the two rival factions have belatedly realised that they cannot make headway against Israel as long as they are politically and geographically divided.
Ordinary Palestinians are drawing the same conclusion: in the face of tanks and fighter jets, Palestinian strength lies in a unified national liberation movement that refuses to be defined by Israel's policies of fragmentation.
The third lesson is that Israel has relied on relative quiet on its borders to enforce the occupations of the West Bank, Jerusalem and Gaza. The peace treaties with Egypt and Jordan, in particular, have allowed the Israeli army to divert its energies into controlling the Palestinians under its rule.
But the question is whether Israel has the manpower to deal with coordinated and sustained Palestinian revolts on multiple fronts. Can it withstand such pressure without the resort to mass slaughter of unarmed Palestinian protesters?
The fourth is that the Palestinian refugees are not likely to remain quiet if their interests are sidelined either by Israel, or by a Palestinian bid for statehood at the United Nations in September that fails to address refugees' concerns.
The protesters in Syria and Lebanon showed that they will not be pushed to the margins of the Palestinian Arab Spring. That message will not be lost on either Hamas or Fatah as they begin negotiations to develop a shared strategy over the next few months.
And the fifth lesson is that the scenes of Palestinian defiance on Israel's borders will fuel the imaginations of Palestinians everywhere to start thinking the impossible - just as the Tahrir Square protests galvanised Egyptians into believing they could remove their dictator.
Israel is in a diplomatic and strategic dead end. This weekend it may have got its first taste of the likely future.
Jonathan Cook is The National's correspondent in Nazareth. His latest book is Disappearing Palestine