Israel had to cook up a convincing reason to justify arbitrarily preventing some 200 people from crossing from the Gaza Strip to the West Bank. After all, this isn't an attempt to infiltrate Israel, but a demand that Israel uphold an old commitment regarding the provision of safe passage between Gaza and the West Bank.

The 40 minutes it takes to drive from the Erez crossing to Tarqumiya is the time that separates life from death for some of those imprisoned at the Erez terminal.

Many explanations are generated when Israel tries to cover up the real reason for its refusal. First they say that the passage poses a security risk, because Israel doesn't want experts in terrorism and the manufacture of Qassam rockets to go from Gaza to the West Bank. Then they say that Fatah officials oppose the move, unless they decide who gets to cross over and who has to go back. And, in general, the situation in Gaza has stabilized anyway, and there's nothing preventing the Gazans from going home.

But the real motivation peeps through the justifications: the fear that the Palestinians will take advantage of the situation and try to storm the crossing point to get to Israel. That was also the rationale for banning ambulances from going in to evacuate the wounded.

The scenario Israelis have dreaded for years, in which hundreds of thousands of refugees march to their destroyed former homes, has popped up once again to frighten Israelis. This scares them so much that they are prepared to cause a humanitarian tragedy and provoke international criticism that sets aside the ruthlessness of Hamas and once again focuses on the cruelty of Israel. The incident at the Erez crossing is just a side effect of the coup that took place in Gaza, but it is highly significant because it shows what Israel is prepared to do to separate the West Bank from Gaza - or, in other words, to continue fragmenting the Palestinian people.

Gaza's isolation, symbolized by the Erez crossing tragedy, is the latest in a series of actions to segregate and crush the Palestinians following the 1948 war. Ironically, these actions have continued with and been enabled by Palestinian assistance.

Israelis are so used to the idea of separating the West Bank from Gaza that their actions require no premeditation. The crossing is closed automatically, the old excuses are offered, and the separation itself is depicted as a major victory. After all, a large chunk has once again been cut off from the Palestinian people, among whom hostility and hared have been engendered.

That's what happened after 1948, when a rift was created between the "1948 Arabs" and the Arabs who remained outside of Israeli control. That's what happened after the 1967 war, when the residents of the territories were cut off from the Palestinian diaspora; this was later institutionalized in the Oslo Accords. And that's what happened in Jerusalem, when the separation wall was built, and the East Jerusalem Arabs were cut off from their surroundings. Now the physical segregation of the Gaza Strip is being institutionalized.

Each of these forms of fragmentation was accompanied by a distinction between "good Arabs" and "bad Arabs" - Israeli Arabs vs. the murderous fedayeen, Arabs in the territories vs. the refugees in the diaspora demanding to return and destroy Israel, East Jerusalem Arabs who live within the fence and oppose terrorism vs. the suicide bombers on the other side of the fence. And now, the Hamas hooligans in Gaza vs. Palestinian Authority Chairman Mahmoud Abbas' government in the West Bank, which deserves all manner of aid.

The next step in the separation will be carried out with the full cooperation of the Palestinians - who, with astonishing submission (possibly due to having no choice in the matter), will accept the identity and the agenda dictated by Israel. Many would like to believe that the isolation of Gaza is destined to fail. But past experience shows that the strength of Israeli action is liable to shape the future. This means the West Bank will be annexed to Israel, and the next Erez refugees really will be infiltrators.