IBBUTZ METZER, Israel, Dec. 11 — The steel gate drew open and, in shorts and sandals, Doron Lieber walked briskly into the chilly, early morning darkness. He walked outside the rusting barrier that the kibbutz children call the "stupid fence," because it did not stop the mysterious terrorist who last month shot dead two of their friends, their friends' mother, and two others before escaping. He walked outside the "clever fence," the silver, electrified one that the Israeli government installed immediately afterward.

A left turn through fields he has farmed for 30 years pointed Mr. Lieber toward the limestone hills and olive groves of the West Bank, which Israel occupied in 1967 and where Palestinians dream of a state of their own. The boundary was less than half a mile away, silhouetted against a rising sun.

Mr. Lieber has new companions on his thrice-weekly walks — trucks that bounce back and forth to the 50-yard-wide gash that Israeli bulldozers have opened inside the boundary of the West Bank. It is the construction site for a separation wall or fence — both terms are used — planned to stretch at least 70 miles, though its precise path is still being debated. Another fence is under construction to envelop Jerusalem.

Under Prime Minister Ariel Sharon, Israel's master builder, Israelis are transforming the land at the root of their conflict with the Palestinians at a rate unequaled since they first occupied the West Bank and Gaza Strip. Settlers have built dozens of outposts on far-flung hills, spreading their handhold across the West Bank. Soldiers have dug ditches and strung barbed-wire fences around Palestinian cities.

But those efforts shrink beside the wall. With cement, guard posts and an electrified warning fence, the Israelis are seeking to split the two populations apart, creating a physical separation as stark as the social one has become.

From the Palestinian side, the wall looks like a land grab, as clear and pure as hate.

But from the Israeli side, its meaning is more layered. The wall represents a tortured compromise with the politics, values and history of Israeli Jews. On the one hand, fences evoke in Israel the pioneering ethos of the state's origins in small, protected communities. But on the other, they echo the European horror — the camps surrounded by barbed wire — that spurred Israel's creation.

Out of these conflicting influences, the wall is developing as an uneasy hybrid. It is a separation fence that still mixes both peoples on each side — in smaller, fenced enclosures. It is a boundary fence that does not create the internationally recognized border that many Israelis want.

Although he defies the logic of the fence with his pre-dawn walks in the open, Mr. Lieber, like most Israelis, is reaching a separate peace with it. He has accepted the growing barrier as necessary, he said, at least for "a few tens of years" to come.

This has been a year of separation, of division. Violence in the Middle East has pushed Israelis and Palestinians farther and farther apart and made hopes of reconciliation — seemingly so reasonable just a few years ago — look vain. Liberals like Mr. Lieber, still yearning for a new Middle East but ever more isolated in an Israel dominated by the right, have come to countenance the wisdom of walls.

Tom Segev, a dovish Israeli historian, called the idea of separation "a kind of magic medicine" that "reflects desperation."

"The whole concept of the fence is so interesting, because it demonstrates how there really is no solution to the conflict at this time," Mr. Segev said. "It's a conflict that can be managed, but it's a conflict that can't be solved."

Mr. Lieber believes Israel is making a historic mistake by building the wall through Palestinian fields, rather than right on top of the West Bank boundary.

"Before the fence, we lived here like good neighbors," he said, after the quiet returned in the dusty wake of another jouncing truck. He thinks the location of the fence provoked the attack on the kibbutz.

Moving in the opposite direction, Palestinians still take Mr. Lieber's route to smuggle themselves into Israel. With the Palestinian economy in ruins, most are desperate to work, but a few, security officials say, are eager to blow themselves up.

Mr. Lieber, 47 years old and the father of six, does not carry a weapon. "I'm a man of peace," he said, with an easy grin that lightly mocked the boast. "Whoever carries a gun ends up using it."

Until the attack on Nov. 10, Mr. Lieber believed that such attitudes, and the relations they helped nurture between the kibbutz and neighboring Arab villages, were the only defenses he needed. Now he is unsure. "If I can say it metaphorically, something cracked in here, close to the heart," he said, putting one palm against his chest.

The killings have cast an enduring shadow over this tranquil enclave, which today marked the close of the 30-day ritual mourning period for the two boys. They have darkened the world view of a collective that was already struggling to find its place in a new, harder Israel, where the old left-wing pioneer dreams of a democratic, secular Jewish society at home in the Middle East have been eclipsed by the extremism and harshness that violence generates.

In the airy kibbutz kindergarten is an alphabet chart in Hebrew, Arabic and English, recalling the possibility-filled years, not so long ago, of the dying Oslo peace agreement: "R" is for respect, "N" is for Norway, "H" is for hope. Nearby, children now play at catching the vanished gunman, dreaming up robots and Pokemon creatures to hunt him down.

Chosen for Attack

Unlike Palestinian gunmen who have wildly sprayed buses or settlements, the killer who attacked Metzer had the discipline to reach the kibbutz's heart before opening fire.

First he killed Tirza Damari, 42, out for a late-night walk with her boyfriend, who escaped. Then the gunman ran to the home of Revital Ohayon, 34, a single mother who had rented here because it was a nurturing environment for her boys, Matan, 5, and Noam, 4. Her home was the converted children's house, where all the kibbutz children slept until a few years ago.

The man tried to burst through the front door; the gash he left is still there, above the small pairs of boots and sandals that still wait. He made his way to his right, past the slide in the playground, climbed through a window, and killed all three.

Back outside, he killed Yitzhak Drori, 44, the kibbutz secretary, who was driving to the scene. The gunman then apparently escaped over the fence.

Residents of Metzer believe the kibbutz was a target because it was an example of co-existence. "They wanted to make a statement," said Dov Avital, a kibbutz leader.

Al Aksa Martyrs Brigades, a militant group connected to the Fatah faction of the Palestinian leader, Yasir Arafat, claimed responsibility for the killings, which came the night after Fatah representatives met in Cairo with leaders of the fundamentalist group Hamas in a bid to halt attacks in pre-1967 Israel. Metzer is in pre-1967 Israel.

At issue in the continuing talks, mediated by the European Union, are questions of strategy, ideology and the clarity of the Palestinian cause. Some Fatah leaders believe that by attacking only Israeli soldiers and settlers in the West Bank and Gaza, Palestinians would signal that they are fighting occupation, not to destroy Israel.

But Hamas wants to destroy Israel. What the Aksa Brigades want, and even if they know what that might be, is murkier.

"It was a technical mistake," said a 27-year-old Aksa spokesman in the West Bank city of Tulkarm, referring to the Metzer attack. "You're in a position where it's mixed borders. It was night. They didn't know where they were," said the man, who declined to be identified.

Israeli security officials say that the attack originated from Tulkarm. The army arrested a man they identified as the mastermind, Muhammad Naifeh, but it has yet to find the chief suspect, Sirhan Sirhan, 19.

The Aksa spokesman said that his group had "severe discussions" after the attack, and was trying to restrict violence to the West Bank. But, he acknowledged that, with Tulkarm regularly under curfew and emotions running hot, there was still some dispute between "the political and military wings of Fatah."

Another member of Al Aksa, Jamal Yehiyeh, said his view of the '67 line had changed. In a Tulkarm street last month, as he kept an anxious eye out for Israeli patrols, Mr. Yehiyeh said he was once enthusiastic about the Oslo vision of two states.

But just that morning, he said, he saw six Palestinian bodies, including children, in the morgue. "We paid too heavy a price," he said, as the conversation turned to Metzer. "The Israelis who are living here who want peace, they should go back to their countries."

Overhearing, Ali Abu Habli, a Tulkarm lawyer, angrily objected. "Our religion, our values conflict with that," he said, his voice rising as Mr. Yehiyeh shook his head. "The Israelis are killing our children, our women, our men. I don't want to reach the point where we are treating them the way they treat us."

A few days later, Israeli forces attempted to arrest Mr. Yehiyeh. He escaped, shot in the hand.

The village of Qaffin, just north of Tulkarm, is not seen by Israel as a hot spot. It lies 10 minutes' walk east of Metzer, past the crumbling concrete posts that mark the West Bank boundary and then across the construction site for the wall.

Taisir Harasheh, the mayor, said that he would believe that the Israelis were concerned about security if they were building the fence on the Green Line, as the West Bank line has been known ever since it was first sketched on a map in green ink after the 1948 war that followed Israel's creation.

Instead, the wall's path has already sliced through the village's olive groves, uprooting trees just before the harvest, and Mayor Harasheh said it would block the village of 9,000 people from 60 percent of its land. "If you make your neighbor hungry, you give him motivation to fight you," he said.

Most of the men in the village once worked in Israel, earning up to $50 a day in construction. A handful still works in Metzer's fields. Most residents survive now on savings, help from relatives abroad, and agriculture.

When Israeli forces posted maps on olive trees depicting the wall's route, villagers panicked. The plans called for a 55-yard-wide strip through almost four miles of village land. They described a concrete barrier 3 feet high, topped by more than 25 feet of electrified warning fence and flanked by asphalt roads.

Israel offered some compensation for land under the fence, but not for village land on the Israeli side. A gate would let farmers reach their trees, Israel promised. Villagers expect that gate to be shut when there is an attack. They expect it to stay shut.

Those whose land has been bulldozed have rejected compensation, perhaps out of principle, but also on instructions from the Palestinian Authority, led by Mr. Arafat.

Mayor Harasheh is a marine engineer who speaks fluent English and has taught himself Hebrew. He spent years traveling the world on ships.

As dump trucks leveled the site, which resembled an endless jet runway, the mayor could see the loom of the Mediterranean, unreachable but less than eight miles away. Before the 1948 war, Qaffin's land stretched almost that far. Metzer sits on land the village lost then.

"I look at the horizon, and I feel really depressed," Mayor Harasheh said. "I don't see any solutions."

One of several armed Israeli guards approached the mayor. Behind him trailed another guard, with an armload of oranges from the village trees. The guard told the mayor that village children had been pelting his men with stones.

"I'm telling you, please deal with the situation. It's better than having someone injured," the guard said.

"The kids don't listen," Mayor Harasheh replied sadly, in Hebrew.

The Dream of Co-Existence

Among the first projects of the founders of Kibbutz Metzer was a fence. The yellowed duty roster from Metzer's first day — Sept. 8, 1953 — records that Dov Cier had guard duty.

While the fence and guards sent one message, the kibbutzniks tried to send another, and so did their neighbors. "We dreamed," Mr. Cier, 72, recalled the other day after lunch in the kibbutz cafeteria. "This was the idea of socialism. We believe in brotherhood between people."

On that first day, the people of the neighboring Israeli Arab village of Meisir, which has no fence, brought the kibbutz water. Now, the water systems of the two communities are joined.

Mr. Cier and the rest of the kibbutz's founders came from South America, and members prided themselves on remaining friendly, as Israeli society grew angrier and more afraid.

The kibbutz, whose very name means border, used to supplement its income by offering "the school for co-existence," giving tours to Jewish tourists and schoolchildren of its grounds and then of Meisir. But though Metzer could once sell co-existence, no one is buying it anymore, and the business has dried up.

Like all the kibbutzim, Metzer, which has about 210 members, is struggling to fit into modern Israel, economically and socially.

These people were, in Mr. Segev's phrase, "the original nobility of Zionism." But as the socialist ideals faded, as Zionist models changed, the kibbutz children found themselves born into a loving but sometimes suffocating world. They yearned for more freedom. So they left.

Hoping to attract younger members, the graying kibbutzniks are adapting their formula. Members still contribute all they earn to the collective, but those who give more get more back in their personal budgets. Children live with their families, rather than together in a "children's house."

Having struggled with a generational divide, some kibbutzniks worry about the hold of Israel on its young. They speak of a cynical generation with less certainty about the Zionist cause. As he watched the trucks rumble toward the construction site from his patio here, Ben-Zion Hevroni said that for that reason, the new fence must become a border.

"Otherwise, I think there is no chance for us," he said, with great weariness. "All this idea of the Zionists, to come and build a homeland after 2,000 years, to live in a place called Israel and tah, tah, tah — all this will disappear. People are getting more and more cynical."

Before the attack here, Kibbutz Metzer pressed the Israeli Army to shift the fence the fairly short distance to the Green Line, to save the orchards of Palestinian Qaffin, even at some cost to its own land.

That effort has lost steam. "You know, I don't mind now about Qaffin," said Mr. Hevroni's wife, Nava, who found herself shielding her 8-year-old daughter with her own body during the attack. "I just want the wall."

The wall reflects the complexity of Israeli politics and the way religion infuses debate: An idea that gathered force on the left, it is the product of a hard-line right-wing government, yet some of its most vehement critics are of the right themselves.

Israel's military leaders insist the fence has no political message, only a security function. Yet, regarding the West Bank as their biblical birthright or as a security buffer against invasion, Israeli hawks fear that the wall will become a de facto border.

They also worry about settlers who may be left on the other side. These concerns help explain the wall's winding, still tentative route, which largely avoids the Green Line and encloses some Israeli settlers, while also trapping thousands of Palestinians on Israel's side.

Mr. Hevroni, whose first name means "son of Zion," has a brother, Israel, who is a settler. Ben-Zion Hevroni, 53, said that he often wondered, in his many years as a soldier and reservist, if he would be dispatched to retrieve Israel at rifle point. Now he hopes others will do it.

He said he was by no means certain that peace would come if Israel departed the West Bank. "But I don't care," he continued. "If there is a border, I have a moral right to fight for my country. I don't feel it now, with my brother on the other side."

If the settlers are forced out of the West Bank, he continued, "I will educate the next generation: `It's O.K. This is your country.' "

Children in the Conflict

Ayala Yichyeh has noticed that it is when they are happiest that the pupils in her kindergarten class remember their friends Matan and Noam. At a recent birthday party, the children wound up talking with their teacher "about whether you could do a birthday for a child who was dead."

Mrs. Yichyeh, a 47-year-old mother of 5 and a member of the kibbutz for 30 years, is left with 16 pupils, in a sun-filled class merrily strewn with simple toys — blocks, dolls, a discarded gas mask. There is a "peace corner" for children to talk through disputes: one yellow chair is painted with lips, another with an ear, a third with a heart; the children switch seats as they take turns speaking, listening, and feeling.

At 5 and 4, the ages of Matan and Noam, children are at a cusp, perceiving more than they can quite understand, understanding more, perhaps, than they can quite express. Against a classroom wall, one child's drawing portrays a night sky and a house. Beside the house, a menacing figure hovers above a chaotic swirl of scribbled lines.

The children know the killer is at large. Whenever Gil Hovar returns from reserve duty in Gaza, his son Nadav asks if he has killed the terrorist. Mr. Hovar tries to explain that he would prefer that the man be arrested, not killed.

Mrs. Yichyeh took the children to see the site for the wall. "I have to give them something to feel better," she said. "They are very afraid."

Last year, Mrs. Yichyeh's class held four joint sessions with a class from Meisir, the Israeli Arab village. This fall, a session was planned to teach the children about the olive harvest, but it was postponed after a suicide bomber struck a bus within earshot of Metzer.

Mrs. Yichyeh said she is determined to do something jointly this year. But a few parents are balking, which is perhaps hard for some in this idealistic place to admit.

"Some of the parents — not all of them — some of them told me — very few, but there are some parents — they told me they're afraid, not from the people of Meisir, but that someone could come across the border and do something to our children," she said.

Mrs. Yichyeh said it was important to teach the Jewish and Arab children that "they are equal, and they are different. They are not the same children, but they are our children."

In Meisir, one of the kindergarten teachers, Aida Abu Rkiya, 43, also looks forward to a joint session. "We found that the language was not a barrier," she said of last year's classes. "They were taking each other's hands and playing."

She said that the morning after the Metzer attack, the teachers began as usual by asking the 26 children how they felt. "Some said, `We aren't happy today because the kids were killed in the kibbutz,' " she said. Villagers paid condolence calls on the kibbutz.

Israel, a country of six million, has an Arab minority of about one million. Mrs. Abu Rkiya used to participate in Metzer's "school for co-existence," and she was amused by the astonishment of Jewish visitors that the Arabs had computers and ate similar food.

Mrs. Abu Rkiya said that her pupils talked about what they saw on TV. "They ask a lot of questions about why the army raided Tulkarm," she said, "why they killed a Palestinian." But they had not begun talking about the fence, she said.

The "Compassion" kindergarten in the Palestinian village Qaffin does not have the resources of its counterparts, and it does no joint sessions with different and equal children. A few drawings of the cartoon cat Sylvester adorn the walls. The teacher, Fakhrieh Ammar, 35, contends with 70 children in two classes.

Her pupils did not mention the attack in Metzer, she said. But the children do have impressions of the conflict, she said. One boy said that soldiers raided his home at night and arrested his uncle. Another reported that his father had been detained for two days while crossing the Green Line for work. Some children were helping in the orchards when the soldiers arrived to clear the area for the start of construction on the fence.

The children here want to grow up to be soldiers, she said, not understanding that they are Palestinian and the soldiers are Israeli. For them, she thinks, being a soldier means being powerful, unassailable.

"They see things on the TV, and on the ground, and they start asking: `Why?' " Mrs. Ammar said.

2 Small Tombstones

Avi Ohayon, the father of Matan and Noam, had not encountered death before the loss of his children, and he says he "didn't know where to put the pain."

"I just miss them. I miss them," he said. "I miss hugging them, I miss playing with them. I miss their smiles. I miss their being there for me. That's why I say everything in my life has been ruined."

His voice catches. "I must have done something very wrong."

On a Thursday evening, Mr. Ohayon, 34, sits with his legs tucked underneath him on a futon couch in his modest apartment in the seaside town of Caesarea. He wears blue jeans and a white T-shirt. He has a wispy black beard, because he is obeying the ritual and not shaving during the 30 days after the deaths of his sons and his ex-wife, his best friend since he was 16.

The television is on, but muted. A colt runs silently through a field. The album cover of Pink Floyd's "The Wall" is propped near Mr. Ohayon's stereo.

Mr. Ohayon, who works as an editor for Israel's Channel 2 television, talks about strangers' pitying glances when he buys cigarettes. He talks about watching parents with their children on the platform as he catches a train, one of his sons' favorite excursions. He talks about picking out small tombstones.

"I had to go and see rocks and say, `Wow, this rock is exactly for my son. This stone is exactly what Noam would like.' " There was not enough space for the lines he wanted inscribed.

He has not returned to work, because his job requires his total concentration. "If I'm concentrating, I'm afraid I'll forget my kids for 15 minutes," he says, "and it frightens me." He is scared all the time now.

Mr. Ohayon has developed a roll of film he found after the boys were killed. The pictures show the boys on vacation in Eilat: clowning with Popsicle sticks, sleeping curled up together on a bed. In one grinning pose, Noam reveals a missing front tooth.

In his sorrow, Mr. Ohayon has started thinking about how to solve the conflict. Asked about politics, he talks about fences. On the table before him is a two-year-old report by the Israeli comptroller about the risks of a fence along the West Bank. With bitterness, Mr. Ohayon says that while politics delayed the project, those risks — international criticism, increased suicide attacks — were realized anyway.

He has concluded that Israel is stuck, rotating governments as it has oscillated for the last 10 years between left-wing and right-wing solutions, both of which have failed.

There must, he suggests, be a third option. Otherwise Israel is waiting for "a thousand funerals" — for a terrorist attack so devastating that the military would respond with overwhelming force. That attack, he muses, could be 30 seconds away.

So why wait? "To solve the problem means thinking about us," he says. "Not what we are willing to give, but what we want for ourselves. Not giving 20 percent of the territories for their promise not to kill anyone outside the Green Line, not to give 50 percent of the territories for their promise to stop terror, not to give 90 percent for their promise for peace. We should stop thinking about giving, and start thinking what do we want for ourselves."

Pain appears to be hardening Mr. Ohayon, as it is hardening many on the other side of the wall that is taking form.

Israel could hold on to the territories, Mr. Ohayon suggests, and accept three million Palestinians within those borders, or draw the line some place else. "But," he said, "Make a border, not a fence that makes little ghettos."