Ariel Sharon’s Gaza disengagement plan looks to be in greater trouble from day to day. Added to the still simmering anti-disengagement rebellion in Mr. Sharon’s Likud; added to his problems in forming a new coalition that would include religious parties in which anti-disengagement emotions are strong; added to the settlers’ threats to resist evacuation both passively and by force, the prime minister is now faced by a new specter – the growing possibility that many soldiers in the Israeli army, which will have to do much of the evacuating, may refuse orders to take part in it.

Almost all of the soldiers who might go to such an extreme are religious themselves, the products of modern Orthodox homes and a modern Orthodox educational system. The reason a mutiny on their part, whether spontaneous or organized, would be so serious is that Israel’s modern Orthodox community, once underrepresented in the army, is now overrepresented in it, particularly in its officer corps.

Observant Jews make up somewhere between a quarter to a fifth of Israel’s population, and since close to half of them are ultra-Orthodox and do not serve in the army at all, the percentage in the army’s ranks of those who do should, ostensibly, be low. And yet over the years, it has grown increasingly and disproportionately higher.

There are two reasons for this, the obverse sides, as it were, of the same coin. The one side is that the years have seen a slow but steady erosion in the motivation of young, nonreligious Israelis to serve in both the regular and the professional army. The decline of nationalism in Israel’s secular society, the trend in it toward consumerism and individualism, the disapproval felt by much of it for the prolonged military occupation of the West Bank and Gaza and for the Jewish settlements there – all have combined to make army service less attractive. Even at the 18-year-old conscription level, at which in theory every Israeli youngster is required to give three years of his life to the military, the number of evaders has increased noticeably.

And at the same time, the trend in the modern Orthodox community has been the opposite. Once upon a time, this community took it for granted that the elite positions in Israel’s army – its pilots, commando units, and combat officers – were not for it. They were for kibbutzniks, moshavniks, Israelis from the secular youth movements – the cream of secular Israeli society.

Yet the last several decades have seen this attitude change as the religious community, largely through its identification with and participation in the settler movement, has come to view itself, no longer as bringing up the rear of Zionist activism in Israel, but as its spearhead and avant-garde – even as its last bastion.

Today, the modern Orthodox community is heavily represented everywhere in the army. Whereas once soldiers belonging to it were largely concentrated in all-Orthodox units connected to what are known in Israel as the yeshivot hesder, yeshivas that send their students to the military, many are now in command positions in largely secular units, too. This is what makes the prospect of a mass Orthodox mutiny so worrisome.

It is worrisome not only for the government of Israel and its army. It is worrisome for the soldiers who might be involved in it, too – and not just because the refusal to obey orders is the gravest of offenses in any army, one often punishable in wartime by death. Besides jeopardizing their practical future, the choice these soldiers may have to face in a few months threatens to bring their inner world crashing down.

From its inception in the late 19th century, the modern Orthodox community in Israel has defined itself by two equally firm commitments: the commitment to Zionism and a Jewish state, and the commitment to Jewish tradition and a religiously observant way of life. It was, indeed, the belief that these two things were compatible that has distinguished modern Orthodoxy in Israel from ultra-Orthodoxy, which has always held that they were not.

Now, for the first time, the modern Orthodox community is facing the possibility that the compatibility it has believed in may prove to be illusory. It is caught between, on the one hand, a democratically elected government of Israel that has decided to evacuate Jewish settlements from part of the land of Israel, and, on the other hand, its own rabbis and religious leaders, who have ruled that not an inch of this land may be surrendered and that no Jew is allowed to collaborate in doing so.

This is a religious and intellectual crisis of the first order for hundreds of thousands of Israeli Jews, many of whom serve in the regular army, many more of whom are in the reserves, and even more of whom are the parents, friends, and relatives of these men. In the terms in which it has been presented to them by their own leadership, they must now choose between being loyal to Judaism and disloyal to a Jewish state or being loyal to a Jewish state and disloyal to Judaism.

It is also, needless to say, a crisis for the Jewish state itself. Mass military disobedience next summer, when the withdrawal from Gaza is scheduled to take place, will be a traumatic event of a kind never experienced before in Israel, the repercussions of which can only be enormous.

There is not much time left in which to avoid this collision. Yet how is this to be done without either the government giving in to the settlers or the settlers giving in to the government, two scenarios that at the moment seem equally improbable?

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