A powerful Israeli war machine, following a sophisticated operational timetable, continued to advance June 7 on Palestinian forces in southern Lebanon.
Israeli authorities maintained a deliberate news blackout over much of the operation, but the strategy appeared aimed not just at pushing the Palestinians out of artillery range of Israel's border, but at the destruction of as much of the Palestinian armed strength as possible.
Fast-moving columns penetrated deep into south Lebanon, bypassing pockets of resistance in order to close off escape routes.
Simultaneously, according to foreign reports, Israeli commando units landed behind Palestinian lines by boat and helicopter along the coast south of Beirut.
An Israeli communique said that mop-up operations are under way in southern Lebanon.
Israeli authorities specifically acknowledged capturing the crusader fortress of Beaufort on a ridge overlooking Israeli settlements in the upper Galilee. The fortress has served as a forward artillery observation point for the Palestine Liberation Organization. Over the years the castle has withstood heavy Israeli bombing and artillery strikes.
In what an Israeli officer described as a bold and swift operation, an Israeli unit captured the heavily defended position before dawn June 7 and raised the Israeli flag over it.
Israeli Prime Minister Menachem Begin, monitoring the operation from an Army command post inside the Israeli border, told the commander of the Lebanese Christians in southern Lebanon, Maj. Saad Haddad, ''The Beaufort is yours.''
The fortress has dominated the enclave controlled by Major Haddad, whose small force is virtually an arm of the Israeli Army.
When the Israeli Army last entered southern Lebanon in force in 1978, that was a straightforward pushback, and the bulk of Palestinian forces in southern Lebanon managed to escape. Israel has issued no casualty figures in the current operation for its own forces or the Palestinians.
A leading Knesset member of the ruling Likud Party, Ronnie Milo, said on Israel radio that the Army is encircling the coastal cities of Tyre and Sidon rather than rushing them in order to minimize Israeli casualties.
Hovering over the operation is the uncertainty over whether the Syrian Army will join in the fighting against Israel. The Syrian Army is believed to have 20,000 to 30,000 men in Lebanon and large forces just across its own border.
The Israelis have signaled in various pronouncements by chief of staff Gen. Rafael Eitan and other leaders that they wish to avoid any clash with the Syrians.
Troops on the right wing of the Israeli drive have been ordered to stay clear of the Syrian Army positions in the area. Israeli Air Force pilots have likewise given a wide berth to the Syrian lines. Syrian reports of artillery clashes with Israeli forces have been played down by Israelis.
The Israelis have said the reports were either wrong or that if clashes took place, they were a nominal gesture by Syria toward the Palestinians that will not necessarily escalate into a full-scale confrontation with Israel.
Israeli military officials have warned, however, that if the Syrians do intervene, Israel would react strongly.
On the Golan Heights June 7 a Canadian officer with the UN peace-keeping force separating the Israelis and Syrians said there was no unusual movement of troops on either side of the border. But there was a Syrian-Israeli air encounter, with Israeli warplanes shooting down a Syrian MIG-23.
On the Israeli side of that border, farmers in kibbutzim worked their fields. That was unlike the situation along Israel's border with Lebanon, where the population has been in shelter since Friday, when the Palestinians and Israelis began exchanging artillery fire.
The UN forces in southern Lebanon were brushed aside by the Israelis moving through their lines. A Norwegian soldier was killed in what Israeli sources describe as an exchange of fire between Israelis and Palestinians.
The incursion into southern Lebanon was hailed by residents of Israeli border settlements.
''I'm not a complainer,'' said Clara Goldberg, a hotel operator in the border town of Metulla,''but the constant shelling was tough. It was impossible to go on like that.''
The Israeli government has ordered the Army to drive the Palestinians northward 25 miles to put Palestinian artillery out of range of northern Israeli settlements.
The operation has won wide approval in Israel even among numerous Israelis who were initially fearful that the government was leading the country into an unnecessary war for dubious motives.
Mr. Begin, in a letter to President Reagan, declared Israel's intention to pull out after its objectives are met.