KEDUMIM, West Bank -- Thousands of Jews slogged through the late- winter mud of the occupied territories this week to plant seedlings in observance of Tu Bishvat, an arbor day observed in Judaism for more than 2,000 years.

Some saw the young trees they planted as affirming Jewish ownership of the whole of Biblical Israel. Others planted alongside Palestinians, in the path of the controversial separation barrier, and said their effort was a statement of their hope for peace between Israel and a future Palestinians state. Still others refused to plant in disputed ground.

Tu Bishvat was once the most blithely Zionist of Jewish holidays -- an embodiment of the national undertaking to reforest and beautify the homeland -- but this year the observance was fractious and highly political due to steadily intensifying dissension over Israel´s plans to withdraw from the Gaza Strip and parts of the West Bank.

Across Israel´s hyperactive political spectrum, proponents and critics of the pullback -- what Prime Minister Ariel Sharon calls "disengagement" from the Palestinian population -- are warning of a looming showdown that could split the Zionist movement, threaten the unity of the Israel Defense Forces, and even lead to civil war.

"The separation is very, very wrong," said Aviad Hason, 16, one of about 2,000 members of the religious Zionist youth movement Bnei Akiva who came to Kedumim, a Jewish settlement deep in the West Bank and deep in Jewish history, to plant trees on Tuesday, the holiday. "I came here to plant because I want to make roots here. It is part of Israel."

Such sentiments are nothing new. According to numerous polls, this is a minority view -- though a very substantial minority, perhaps 45 percent of Jewish Israelis. It´s what the young resident of the Israeli town of Kadmina, who is due to join the army in less than two years, said next that is setting off alarm bells throughout the society.

"If I am ordered to evacuate" Jewish settlers from the occupied territories "I will refuse," Hason said flatly. "I will not evacuate my own brothers. I have my ideals to live up to."

Interviews with numerous youths in the 80,000-member organization suggest they are unanimous in opposing the disengagement, and deeply split over whether, when they are called up for military service, they will obey orders to make the series of evacuations that will be necessary for the eventual creation of a Palestinian state.

"I would fight for this land," said Naor Harari, 17, who is due for induction this year and is against the disengagement plan. "But if the government says soldiers need to do something, I would do it. That´s what it means to have a democratic country."

Hani Mizrahi, 15, disagreed. "All those who refuse -- this shows how much they love their country," she said. "This is the land that the Lord gave to us."

Divisions in the adult population -- among politicians, rabbis, and soldiers -- are similarly deep.

The day before Tu Bishvat, the parliamentary subcommittee drafting compensation arrangements for homeowners and businesspeople who are to be evacuated next summer held a hearing on compensation issues in Gush Katif, the principal bloc of settlements in Gaza, and the three subcommittee members were asked to plant trees in the settlements in observance of the holiday.

The member who belonged to a left-wing party that advocates Israeli withdrawal from all the occupied territories flatly refused. The member from the center-left Labor party reluctantly agreed. The member from the religious-Zionist National Union agreed enthusiastically, blessed the settlers, and told them he hoped to return in future years to enjoy the tree.

The sharply divergent attitudes toward this year´s tree planting "represent certain aspects of the most basic ongoing conflict in Israeli society," said Daniella Weiss, mayor of Kedumim and a leading voice against disengagement. "The issue is what is Zionism at this point in history. We are at an interesting and crucial crossroads."

On the one hand, she said, "we have Israel as an independent Jewish state, young, modern, successful, with fine accomplishments in science, technology, many areas. . . . But if there is anything that is really Israel" in the historical and religious sense "it is Jericho and Shechem [Nablus], and Hebron and Bethlehem" -- all cities that loom large in Jewish history and now are virtually entirely populated by Palestinians, many of whom deny that history.

The essential conflict is between a pragmatic approach, embraced by Sharon and his supporters, and a spiritual approach based on Jewish values, she said. "Sharon forgets the main factor of Jewish life in the Holy Land -- the religion itself," Weiss said. "He thinks the religion and the folklore are the spice, not the food itself. He thinks they add to life, we think they are life itself."

Uzi Dayan, a former second in command of the armed forces and an originator of the separation barrier concept, opposes the religious Zionist goals but agrees with Weiss that a crucial moment is approaching.

Withdrawal from the territories that Israel occupied in the Six-Day War of 1967 "is the historic decision of our generation," Dayan said. "It is very controversial. There is a danger that Israel won´t be able to take this decision, which is essential to our existence as a democratic Jewish state," because of the depth of the divisions and the risk of an irreparable schism between secular and religious Zionists.

Citing recent statements by nationalist rabbis encouraging soldiers to refuse orders and side with the settlers, Dayan also asserted that "there is a real possibility of bloodshed."

Unlike most advocates of withdrawal from the territories, Dayan supports the idea of a national referendum on the issue to help build a deeper national consensus in favor of the step. "For such a vital and controversial decision," he said, "I don´t think it should be decided with a single vote [in parliament]. All Israelis should take part in this decision."

Sharon so far has rejected political ploys and demands from the political right and settlers, who are still seeking a referendum despite polls indicating they would lose. Sharon´s supporters say this is because the prime minister believes they are playing for time in hopes that unforeseen developments will force new elections or shift public opinion before he can get the withdrawal underway.

The opposition does not deny this.

"We are believers," said Moti Sender, a resident of Ganei Tal in the Gaza Strip who organized a large tree-planting there this week. "Things can change in the blink of an eye. Look what happened in Asia three weeks ago. . . . We human beings do not control everything. We continue to live our way of life. We believe things will change."

But Binyamin Elon, the National Union parliamentarian who so enthusiastically planted a tree in Gaza and blessed the settlers this week, is now less sure that Sharon´s plans can be stopped than he was when the plan passed the Knesset in late October.

"This man [Sharon] has experience and I am afraid he may be able to manipulate things and continue," Elon said.

He called the task of drafting compensation provisions for settlers who are to be evacuated "the most difficult job I have had in the Knesset."

"How much for a house? How much for a business? You try to stop this" withdrawal, he said, "but God forbid it should come, you have to be prepared to deal with it."

Globe correspondent Alon Tuval contributed to this report. Charles A. Radin can be reached at radin@globe.com. (Copyright 2005 The New York Times Company 01/28/05)