Like a man who has been holding his breath for a long time, Israel began its physical disengagement from the Gaza Strip yesterday with an almost audible sigh – of relief, of pain, of anxiety, of sorrow, but in any case, of many months of waiting that have at last come to an end.

It was not, of course, a coincidence that disengagement began on the day following the Ninth of Av, the traditional fast day mourning the destruction of the First and Second Temples. Although the settlers wanted it that way for symbolic reasons, the exigencies of the secular calendar were working on their behalf. The government chose to carry out the evacuation of the Gaza settlements during the summer vacation, when the lives of the families and schoolchildren involved would be least disrupted, and since it did not want the fast day to come in the middle of the process, it decided to start the morning after.

The evacuation of the Gaza settlements is not, despite attempts to portray it as such, a historic catastrophe like the Temples’ destruction. Forcing 8,000 people to leave their homes cannot be pleasant, but many countries have relocated larger numbers of inhabitants for peaceful goals like dam construction or urban renewal without their personal tragedies being interpreted as national ones.

And yet even for the clear majority of Israelis who have supported disengagement, like myself, this is a mournful day – and not only because thousands of individuals are about to lose their homes.

Nor is it only so because of the deep national schism in the Israeli public’s response to disengagement – a schism between the political right and the political left, and between religiously observant Jews and nonobservant Jews. This schism existed before disengagement was put on the national agenda and will continue to exist and perhaps even deepen in the years to come; and disengagement has merely exacerbated – in some respects, it is to be hoped, temporarily – its symptoms.

No, there are other things to mourn, too. One is that – as many of the critics of disengagement have rightly pointed out – the unilateral Israeli withdrawal from Gaza is less a step toward true peace with the Palestinians than a renunciation of the belief in such a peace. Although Israel’s unilateralism in Gaza has many justifications, demographic, military, and moral, it also reflects a deep despair of the possibility of ever negotiating a mutually satisfactory agreement with the Palestinian leadership. There would indeed be little point to disengagement if such despair did not (I would say for good reasons) exist.

There is also the unique character of the Gaza settlements. It is ironic that of all the Jewish inhabitants of the disputed territories, those in Gaza, with a few exceptions, represent the settler movement at its very best. They built their homes on state-owned lands whose utilization did not call for expropriation or the dispossession of local inhabitants. They have been among the most ideologically moderate of the settlers and have on the whole gotten along well with their Palestinian neighbors. And they have been moderate, too, in their relations with one another. The “Katif Bloc,” the southeast corner of the Gaza Strip in which most of the Gaza settlers lived, was known for its many villages in which religious and secular Jews lived side-by-side amicably and with little friction.

If anyone was the salt of the earth of the settler movement it was they – especially because they alone of settlers anywhere lived from the land and not just on it, practicing agriculture on a wide scale. The hothouses and vegetable farms of the Katif Bloc had an international reputation and supplied European chefs with some of their best products. The Gaza settlers worked hard, lived modestly, and minded their own business, and if personal merit had anything to do with it, they would be the last of any settler population to deserve eviction.

Indeed, though it would seem a truism to say today that Jewish settlement in an impoverished and thickly populated Palestinian area like Gaza was a foolish mistake to begin with, the settlements in Gaza were closer to the classical Labor Zionist model than any in the West Bank. The decision to locate them in Gaza may have been romantic and irrational, but it was true to the most basic of Zionist instincts that guided Jewish settlement in Palestine from the late 19th century on: to look for empty spaces in the land of Israel and to get Jews to build their homes in them and make them productive.

Zionism was always a movement of construction. Although from the point of view of Palestine’s Arabs it may have been a terribly destructive force, this was never how it seemed to Jews. Unlike other 20th-century ideologies, it never set out to tear down anything, but only to build, to plant, to settle, “dunam by dunam and goat by goat,” as the old Labor Zionist slogan went. The Katif Bloc settlements were true to this impulse. Yes, someone should have thought harder about whether, in the long run, they would be geopolitically viable, but that someone would have had the entire tradition of Zionist pioneering going against him.

It is a mournful day when a Zionist state has to destroy what it has built; it goes deeply against the grain. This is why even those of us who believe that the disengagement from Gaza is crucial for the future welfare of Israel as a Jewish state cannot be happy to see it taking place. One’s mind agrees with the government that is determinedly carrying it out; one’s heart is with the settlers who are clinging to the doorposts of their homes. They deserved a better reward for their labors, and it is not their fault that they have not gotten it.

Mr. Halkin is a contributing editor of The New York Sun.