The northern Galilee was quiet today for the first time in three days as the Israeli Army command said it had forced Palestinian guerrillas far enough north into Lebanon that their artillery could no longer reach Israeli settlements.

The Army chief of staff, Maj. Gen. Rafael Eitan, said his troops had accomplished in the first 24 hours of their invasion into Lebanon what he had expected would take twice as long. With the capture this morning of Beaufort Castle and the surrounding highlands, he said, Israel had forced the guerrillas out of range of all Galilee settlements except those in the narrow panhandle between the borders of Lebanon and the Golan Heights.

The Army command continued a virtual blackout on details of Israeli troop movements in Lebanon, saying only in a communique that the invasion forces "are continuing to root out terrorist nests and sources of fire in southern Lebanon. All of the objectives set for the Israeli defense forces so far have been achieved."

But while Israel's short-term objective in southern Lebanon seemed clear enough--to drive the guerrillas north of the Litani River to the Zahrani River to establish a cordon sanitaire between Palestinian guerrillas and Israeli settlements--the long range goals of the invasion remained far from certain.

Deputy Foreign Minister Yehuda Ben-Meir, responding to a suggestion that the armored columns' pincer movements from the northeast and the southwest appeared designed to encircle the guerrillas as a prelude to a search-and-destroy operation, denied that Israel's objective is to achieve a military solution to the threat from the Palestine Liberation Organization, which Eitan and Defense Minister Ariel Sharon repeatedly have said is necessary.

"We are not trying to effect a military solution to the PLO, or even find a military solution to the PLO in this operation. Eventually, we will remove this scourge from the face of the earth, but for now this is not our aim," Ben-Meir said in an interview.

Ben-Meir was vague about Israel's vision of an eventual political solution to the current conflict. He said, "We have to find a way of being assured. We don't want to suffer casualties again in another operation.

"We must not have a situation in which the PLO will occupy this area with total impunity and the situation will repeat itself. We will insist on this objective being met in any cease-fire arrangement," Ben-Meir added, indicating that a return to the July 24 cease-fire arranged by Habib will not suffice.

Even as reinforced armored columns continued to batter Palestinian positions as far north as the coastal city of Sidon and beyond, Prime Minister Menachem Begin met tonight with U.S. special envoy Philip C. Habib and reportedly told him that Israel will not agree to any cease-fire arrangement that would allow the guerrillas to again move within artillery striking distance of civilian settlements in the northern Galilee.

Following his 90-minute meeting tonight with Begin, Sharon and Foreign Minister Yitzhak Shamir, Habib refused to comment on the situation. A close adviser to the prime minister, however, said Begin told Habib that Israel will withdraw from Lebanon only when it has guarantees the PLO will not return to the south.

Israeli officials said they are aware of the danger of the PLO acquiring new weapons that will extend their range beyond the 25-mile limit set by Begin, including Soviet-built Frog and Scud missiles and SS4s. But they said that this would introduce an entirely new dimension in the Middle East that Israel would have to deal with at the time.

While Israeli officials have been reluctant to discuss specifics of the terms of a political settlement acceptable to them, the most frequently mentioned possibility has been a strengthened U.N. peace-keeping force or even a new multinational force that could be depended upon to keep Palestinian guerrillas out of the 25-mile zone.

In any case, advisers to the prime minister contend, Israel does not relish the prospect of maintaining so far from its border an occupation force of the size that would be needed to contain the guerrillas north of the Zahrani River.

The Army command announced tonight that the invading Israeli forces had captured the Lebanese cities of Tyre and Nabatiyah and had surrounded the coastal city of Sidon. Israeli troops were reported to have landed in amphibious craft north of Sidon, which is 20 miles south of Beirut.

The command later announced that 25 Israeli soldiers had been killed so far, 96 wounded, seven were missing and one was taken prisoner.

Israeli military officials conceded that the advancing armored and infantry brigades were meeting stiff resistance in some sectors, but they denied reports that their troops had clashed with Syrian forces directly. A Syrian-Israeli clash could widen the conflict into a full-scale war.

The Army command said its units that captured the town of Hasbaya were shelled from an area controlled by the Syrians and that the fire had been returned. But an Army spokesman said the Syrians had been assured through diplomatic channels that the Israeli defense forces are not interested in engaging the Syrian Army in Lebanon.

Eitan said, "We intentionally do not go anywhere where there are Syrians, even when there are also Palestinian terrorists there, and we know they are there." However, the Army command reported tonight that Israeli warplanes over Beirut shot down a Syrian Mig23 in a brief dogfight.

The crusader-era Beaufort Castle ruins, situated on a steep cliff overlooking the Litani River and the Galilee, had for years served as a strategic observation post for PLO artillery gunners. Military officials said 30 to 50 guerrillas offered stubborn resistance to the overnight Israeli assault and that the final stages of the battle entailed hand-to-hand fighting.

Begin, in a meeting in Army northern command headquarters with Lebanese Christian militia leader Maj. Saad Haddad today, was reported to have embraced Haddad, saying, "The Beaufort is yours." Haddad's militias, which are participating in the invasion, control, with Israeli support, a narrow enclave just north of the Lebanese-Israeli frontier.

Later in the day, Begin flew by helicopter to Beaufort Castle, where he met with the commander of the assault force and congratulated his troops.

Although the decision of the timing of the invasion and its scope was made in a secret Cabinet meeting Saturday night and formally approved by the ministers in another session hours after the attack the next morning, a decision in principle to secure the northern Galilee appears to have evolved over a much longer period of time.

In a Cabinet meeting last month, a slim majority of the ministers was reported to have favored Sharon's proposal for a massive invasion of southern Lebanon, but Begin, according to Cabinet sources, turned the consensus around and succeeded in adopting for the time being a posture that can only be described as exasperated restraint.

The shooting of a second secretary in Israel's Embassy in Paris last month, preceded by a machine-gun attack on an Israeli purchasing mission in Paris and the disclosure of a plot by the PLO to assassinate the ambassador to Italy resulted in even more pressure on Begin to give the go-ahead for an invasion.

However, the prime minister continued to restrict his responses to warning rhetoric until Shlomo Argov, Israel's ambassador to Great Britain, was shot in London Thursday.

Immediately after that shooting, government officials began warning of a new wave of terrorism against Israeli diplomats abroad and suggested that Israel's capacity for restraint was not unlimited. They also suggested that a major retaliation against the source of the terrorists attacks--which they said was the PLO in Lebanon--would be seen in world opinion as justifiable.

Obtaining a new consensus Saturday night for the final go-ahead of a military plan that had already been charted by Sharon and Eitan appeared to present no obstacles for Begin.

Sharon is said to have assured Begin that the main tactical objectives of "Operation Peace in Galilee" could be achieved with 72 hours.