The significance of Israel's withdrawal from Gaza is obvious: For the first time since the 1967 war, it is setting about to dismantle settlements in an area that Palestinians see as part of their ultimate state, and it is doing so under the leadership of the man who was the architect of the settlement movement, Ariel Sharon.

What is less well-known or understood is that for the first time, Sharon intends to evacuate a part of the external perimeter around the Palestinians. This is an act with far-reaching consequences. Furthermore, Palestinians will likely, for the first time in 38 years, be allowed to come and go without passing Israeli forces.

Palestinians view this lifting of Israeli guards at the border with Egypt as a symbolic and concrete element of their freedom. Success here could spur solutions to similar security-related problems regarding a future Palestinian state. Moreover, the Israeli move would introduce the concept of an active third party in security matters. This is an idea that Israel has been reluctant to adopt. Given the enmity toward Israel's existence inside the Middle East and out, the Zionist ethos has traditionally been predicated on self-reliance.

On the other hand, failure in this first venture could be costly. If Palestinian missiles are brought in that are capable of hitting Israeli cities, alongside the existing crude rockets that hit Israeli border towns, it will bring Israeli military retaliation and make Israelis wary of further withdrawals. Moreover, the international community's support for a two-state solution is predicated on a genuinely demilitarized Palestinian state.

To leave no doubt that Israel is departing Gaza, Sharon has declared that he wants Israeli soldiers to vacate the narrow corridor between southern Gaza and northern Egypt. The risk here is real: Gaza is home to Hamas, an organization that is sworn to Israel's destruction and that the Palestinian Authority has been hesitant to confront. Gaza has been a breeding ground for the smuggling of personnel and weaponry via both overland and underground routes.

To counter the smuggling of weapons, Israel has decided to rely on Egypt. It is counting on Egypt's becoming more motivated and more capable in dealing with such problems. For the fact is that Egypt has an interest in preventing Gaza from becoming an Islamist state or "Hamastan" on its eastern frontier, promoting radicalism that could spill over onto its own soil. And Israel hopes that the deployment of 750 highly trained Egyptian border patrol troops, to which it agreed, will bring success where poorly trained police could not. The current presence on the Egyptian side of the border of a U.S.-led multinational monitoring and observer force (MFO) of several hundred, deployed in the aftermath of the 1979 Egypt-Israel peace treaty, could signal to Cairo that the world is watching how Egypt performs, and it could also clear up any misunderstandings.

Still, the risk remains. Until now, Cairo assumed that Israel would play the heavy in plugging tunnels, but now the onus will be on Egypt. Its main focus will be on Rafah, a divided border town where clans on both sides have made smuggling their livelihood. The number of tunnels between Egypt and Gaza has been staggering. Israel closed more than 100 tunnel openings during the intifada of 2000-04, but this underground industry has yet to be eliminated. Israeli security officials claim that within an 18-month period culminating in mid-2004, there was a treasure trove of known smuggling: two tons of explosives, thousands of AK-47 automatic rifles, hundreds of anti-tank rockets, a few dozen mortars and hundreds of thousands of rounds of ammunition.

There is also concern about above-ground crossings. One idea reportedly under consideration is to have a trusted third party direct the flow of people in and out of Gaza at the current Rafah crossing point and coordinate with Israel to ensure that there is no infiltration of al Qaeda members or other bomb makers. In turn, Israeli personnel, alongside a third party, would supervise the flow of cargo at a separate terminal adjacent to the Israeli border zone.

Who would be the third-party coordinator? It would make sense for it to be a combination of a professional company that has experience with border control management, such as Lloyds of London, and a force such as the MFO that could impose order if necessary and serve as a liaison with governments. Another layer of comfort that could build confidence on all sides would be the regular convening of consultations between Palestinian, Israeli, Egyptian and MFO officers. Indeed, this model had a modicum of success in Naqura, a Lebanese border town, which kept civilians out of the border conflict between Israel and Lebanon in 1996-2000.

In any event, there is much to be done and much at stake in Gaza.

The writer directs the Washington Institute for Near East Policy's project on the Middle East peace process. He is author of the recent study "Engagement Through Disengagement: Gaza and the Potential for Renewed Israeli-Palestinian Peacemaking."