They'd been through it all before so many times - or at least they seemed to give that impression.

Some of the Lebanese civilians and Palestinian guerrillas retreating once again before the Israelis reacted with panic, but most with resignation.

The pattern visible in this mountain village near the toughest only five miles from the Israeli border was repeated throughout the day across southern Lebanon.

Families fled north only to find Israeli fighter-bombers striking at the very urban centers that Israeli leaders had sworn to spare.

The civilian targets ranged from the main guerrilla seaport of Tyre in the south to the town of Damour only 11 miles south of Beirut and a seaside suburb that runs parallel to the main runway of Beirut's international airport.

In the attacks near Beirut, panic seized civilians and officials alike as Israeli jets dropped heavy bombs that collapsed houses and buried inhabitants alive.

For the first time since the end of the Lebanese civil war 17 months ago, the panicky sought refuge in empty Beirut apartments.

Here in this hilltop town the lucky rode out in big American cars with trunks too jammed for the lids to close over belongings or relatives.

Other lucky Palestinians were able to catch rides in military vehicles ferrying troops from the fallen stronghold of Bint Jbeil. That position had long prevented pro-Israeli Lebanese Christian militiamen from establishing a continuous front along much of the border.

The less fortunate refugees made their way on donkeys and mules - or on foot carrying their possessions in plastic bags.

Families that had decided to stay stared out blankly at those hurrying by. It was as if they had finally understood what had spurred those who fled as soon as the Israeli attacks began around midnight.

As for the troops, they did not seem as sullen as might be expected of soldiers who had been subjected to 10 hours of heavy artillery and fighter-bomber attack at Bint Jbeil before being driven out by infantry and tanks.

They did not bother to put much of a pretense of having fought, but some insisted that 100 of their comrades were trapped inside Bint Jbeil and were still resisting.

Occasionally the Israelis fired a mortar or two as if to encourage the Palestinians to keep moving away from the border. They needed no prodding.

As they streamed through the carefully terraced farmland, resplendend in its rain-fed coat of green, a Palestinian officer waved them away from the village nearest to Bint Jbeil. "Get out! This place is next," he shouted.

A Lebanese law student from Bint Jbeil, cardling his Kalashnikov submachine gun, laughed off the Israeli capture of his home town a mile or so up the road.

"In a few days the Israelis will leave," he said.

Who would take their place?

"Their friends among the Lebanese Christians," he answered.

Would he and his Moslem family then be able to move back home?

He scowled and did not answer.

Down the road three guerrillas smiled with pleasure. They carried three parachutes that had held Israeli flares. The trio beamed like schoolgirls as the caressed the material, which could well be used for wedding gowns.

Further down the mountain toward the Mditerranean at Faradounine, a young woman howled and screamed as she sifted through her home which had been hit by an Israeli jet's rockets soon after dawn.

"No Palestinian here," she protested. Yet, the Israeli planes may have been drawn to the area by some Palestinian vehicles. Recent tread marks cut deep into the asphalt.

Offshore from Tyre, four Israeli warships shelled the city, the large Rachadiyeh Palestinian refuge camp nearby and guerrilla military positions high in the mountain.

Palestinian gunners opened up in half-hearted fashion at Israeli Phantoms flying out of range high overhead and taunting them with victory rolls. The image of Israeli military competence contrasted with the guerrillas' inspired amateurism and bravado.

The real urgency, as always in war, was reserved for the ambulances and their howling sirens.

In Tyre alone, doctors in two hospitals reported between 37 and 42 wounded - most of them Lebanese civilians - and two teenagers dead.

A doctor at the Palestinian hospital criticized the Israelis for what he called deliberately obstructing access to the Rachadiyeh camp for more than an hour.

As he spoke two fighter-bombers, the first of a series, dived low over Tyre and dropped at least six heavy bombs. Black dust leaped in the air. The hospital windows rattled. Patients scuttled down halls, screaming and yelling.

Motorists jumped into their cars and headed north five miles to the bridge over the Litani River which to people here had come to symbolize the northern limit of Israeli military interest.

The symbolism was apparently lost on the Israelis.

Far north of the Litani, the Israelis singled out Damour for punishment, apparently on the ground that it had been the base for Saturday's terrorist attack that triggered the Israeli reprisal.

Damour, once a Christian center in an otherwise Moslem area, was badely destroyed by Moslems in January, 1976 in retaliation for a Christian attack against a Moslem enclave in Christian territory.

Many of its new Moslem inhabitants were the survivors of the harrowing Christian siege of Tal Zaatar camp in the summer of 1976.

Israeli Phantoms first dropped a stick of bombs on a seaside banana plantation. Later waves struck along the main street, adding new craters and crushed buildings to the debris left from the 1976 sacking.

Nervous Palestinian troops helped panicky civilians to load up their few belongings once again and head for the supposed safety of Beirut where many took over empty apartments.

Within minutes, Israeli planes hit even nearer to Beirut, flatening 300 to 400 yards of one-and two-story housing.

By preliminary estimate as many as 40 persons - none of them believed to be Palestinian - had perished in the raid. A sudden rumor that the planes were returning sent motorists, firefighters and residents scurrying into their cars in panic.

Close by, at the airport, commercial planes continued to land - just as in the waters off Tyre a large sailboat had paid no attention to the Israeli warships whose guns were pounding away at targets on shore.