Nabil's young wife, Paula, died last month the way people often do in southern Lebanon -- torn apart in her car by a roadside bomb detonated by remote control.

The blast killed all five people in the black BMW, obliterated the car and shredded whatever modest beliefs Nabil had that he was fighting for anything but a lost cause with anything but a disintegrating army.

Nabil is a soldier in the South Lebanon Army, a force that Lebanon's neighbor Israel has armed, paid and deployed for 14 years to help it fight the Iranian-backed guerrillas of Hezbollah, the Islamic "Party of God." Although Hezbollah denied planting the explosive that killed Paula, the group often uses roadside bombs against Israel and its militia allies.

It is a war of attrition that Israel badly wants to end -- if it can only figure out how. The endgame is clouded by fear, the potential for vengeance and the vagaries of diplomacy, but the outcome is no longer in doubt: Israel cannot win militarily, and sooner or later -- perhaps within a year -- it will have to withdraw from the violent strip of territory in southern Lebanon that it created two decades ago in a bid to prevent attacks on northern Israel.

The awkward question of where this leaves Nabil and 2,500 other increasingly demoralized fighters was answered suddenly last week by a surprise declaration by Antoine Lahad, the militia's commander. Lahad, who is close to the Israeli army, announced that his force would retreat from the area of Jazzin, a strategic pocket of fragrant orchards and pine forests that the militia has held since 1985. The retreat began last night.

"We've lost 200 people from around here," said Nabil, soft-spoken and cordial despite the fierce first impression his assault rifle and grenade launcher make. "Now we're pulling out without any security guarantees or anything. Probably nothing will happen for two months or so while people are paying attention, but after that . . . "

Nabil's fear -- shared by Israel and the United States -- is that the eventual withdrawal of the Israeli army and the disintegration of the militia could trigger a bloodbath in southern Lebanon if people there, nearly all of them Christians, are left to the mercies of Hezbollah. The best way to prevent that, analysts say, is for Lebanon's regular army -- for years conspicuously absent from the fighting in the south -- to move in quickly and take control.

The anxiety has intensified in the two weeks since Ehud Barak, a retired general, was elected Israeli prime minister. One of Barak's campaign promises was that Israel will pull its troops out of southern Lebanon within a year, and he has repeated this stance since his victory. Israel has suffered several dozen combat casualties there each year, convincing many Israelis that the war is futile.

Analysts across the Middle East are watching Jazzin closely, particularly the actions of the Lebanese government and Hezbollah. Hezbollah, like many Lebanese, regards militia fighters such as Nabil as traitors, but insists publicly it will not enter Jazzin seeking vengeance. The militia's leadership is wary.

"The situation is, Jazzin just could not handle any more death," Lahad, the commander, said in a news conference yesterday. "Our aim in being in Jazzin was to protect its people, and we hope the government will do the same."

The question of how Israel departs from southern Lebanon and what happens there afterward is critical to the prospects for Middle East peace and entangled in broader, unresolved regional issues.

Chief among them is the role of Syria, a regional power that controls much of what moves in Lebanon, including Hezbollah. Syria insists that any peace deal include the return of the Golan Heights, which it lost to Israel in 1967.

That makes an Israeli pullback doubly complex. For without a broader deal with Syria on the Golan, Israel would be unable to remove its troops from southern Lebanon without risking cross-border attacks on northern Israeli towns by Hezbollah, encouraged by Damascus.

The timing of the militia's decision to leave Jazzin was a surprise, but the fact of it was not.

Hezbollah, handsomely funded and trained by Iran, is a lethal guerrilla force. Helped by an efficient intelligence-gathering operation, it fights a hit-and-run war of roadside bombs and ambushes that has killed about 900 Israeli troops since the mid-1980s and many more militia fighters.

The effect on the South Lebanon Army has been devastating. Its strength in Jazzin, an enclave just north of the Israeli-occupied security zone, has declined from more than 400 fighters a few years ago to fewer than half that today. Some fighters have been slain; today, the Reuters news agency reported that one fighter was killed when a bomb went off shortly after the pullout began. Other militiamen have deserted. None speaks of victory.

"Once we leave, it means these young men who were killed died in vain," said Nabil.

Jazzin itself, once popular as a cool highland retreat for wealthy Lebanese, is a ghost town of silent streets and half-built hotels with a tenth of its prewar population and a shattered economy. Besides the militia, whose fighters draw a monthly salary from Israel of $400 or $500, there is little work.

The militia fighters have all but disappeared from view. Some, including Nabil, will retreat farther south to the Israeli-occupied zone. Others will simply put down their weapons, stay in their homes and await their fate -- trusting in the assurances of the government and Hezbollah.

"We're at the mercy of the Lebanese state and of Lebanese justice," said Edmond Rizk, a Jazzin resident and former government minister. "We're citizens who acted in the absence of state authority in a way that can be judged charitably or harshly. But we had no choice. We did what we could."

Hezbollah, which has termed 1998 and 1999 "the years of the militia's disintegration," has issued repeated calls for South Lebanon Army fighters to desert, and pushed for amnesty for those who do. Those who do not desert, Hezbollah leaders have warned, will be hunted down -- even in their beds.

Still, the group has made soothing statements about its intentions in Jazzin after the militia leaves. "The people of Jazzin are perfectly safe," said Naim Kessem, a white-turbaned cleric who is Hezbollah's second in command.

Having toned down its stated ambition of a decade ago to make Lebanon an Islamic state, Hezbollah's 5,000 to 10,000 fighters are now widely regarded by Lebanese Christians and Muslims alike as a patriotic resistance to the Israeli occupation. Its network of hospitals, clinics and schools has given the group a social base: Hezbollah controls seven seats in the Lebanese parliament.

This has led to hopes that the group can be demilitarized and integrated into Lebanese political life once Israel withdraws. Kessem, the Hezbollah cleric, speaks of the group "shifting priorities" once the war is over, but refuses to guess when that might occur. "As long as there is occupation there will always be resistance," he said. The militia's withdrawal from Jazzin is a sign of things to come, he said. "The end of this group will be soon."

CAPTION: Members of the South Lebanon Army prepare for withdrawal from the Jazzin area, just north of Israeli-occupied zone.