A two-year period of relative calm in the Middle East is being threatened by escalating clashes in the hilly reaches of southern Lebanon, but an all-out war seems unlikely.
The current fight is between the armies of Israel, its "free Lebanon" ally, Maj. Saad Haddad, and a joint force of Palestinians, leftist Lebanese, and Syrians.
Some Middle East analysts here feel the conflict has taken a dangerous turn because of several recent events:
* On Aug. 19, Israeli commandos fought a pitched battle with rival forces near strategic Beaufort Castle in Lebanese territory. Since then, both sides have increased artillery bombardments, disrupting village life in southern Lebanon and northern Israel.
* On Aug. 24, Israeli planes shot down a Syrian MIG-21 in a battle over Lebanese territory -- the first aerial clash between the two countries in 14 months.
* There also were two incidents of terror bombings within Israel, for which Palestinian forces are claiming credit.
Even so, the consensus seems to be that a new Arab-Israeli war is unlikely at this time. Instead, these developments are viewed as signs that rival forces are using the period before the Nov. 4 United States elections to jockey for position while world attention is diverted.
"Arab countries are too divided and too faced with their own internal problems to fight a war right now," commented one Western diplomat Aug. 25. "The Palestinian Liberation Organization [PLO] is still engaged in its quest for recognition and respectability in Europe. Since they have come this far, they probably would not want to risk their gains by being branded again with a violent image," he added.
Still, these analysts concur that a wrong move could engulf the entire region or throw the Balkanized factions within Lebanon into conflict.
The focus of Israeli attention now is Beaufort Castle, a Crusader-era fortress situated on a pinnacle overlooking the Litani River, de facto boundary between Israeli-Haddad troops and pro-Palestinian forces.
Last week, in the heaviest ground fighting since 1978, a 600-soldier Israeli detachment tried, but failed, to take the castle. Prime Minister Menachem Begin promised, however, to send Israeli forces into the area again, saying these are preemptive raids against terrorist staging positions.
Israel's Deputy Defense Minister Mordechai Zipori said that attacks would continue between the "Litani and Zahrani Rivers." Previously, the Litani was considered the northern boundary of Israeli operations.
PLO officials believe the Begin government has three aims in mind:
* To prevent the Palestinians from raiding or shelling northern Israel by keeping them off balance, and draining their resources.
* To direct Arab and world attention away from the shaky Begin administration , the Knesset-proclaimed annexation of east Jerusalem, and the stalled Camp David peace talks.
* To secure access to the Litani, a major water source in the arid region.
Lebanon's ambassador to the United Nations, Ghassan Tueni, says the attacks have caused "near to total disruption" of southern Lebanese social and economic life.
A tour of Nabatiyeh and Arnoun, two of the towns receiving the brunt of the shelling, shows that only half the populations remain. Long-range artillery bombardment of the villages, which had damaged scores of houses and shops, was in progress at the time of the tour.
Beaufort Castle, though severely pounded, appears virtually impregnable because of its commanding position. If Israeli forces were to try again to take it, the task probably would require many more troops and weapons. PLO officials claim the Israelis are building up for such an attempt.
PLO "foreign minister" Farouk Kaddoumi apparently is trying to deter such an event by raising the standard of "Arab unity," but few Arab states rushed to condemn the Israeli attack when it occurred.
Mr. Kaddoumi warned, however, that even with divisiveness in the Arab ranks, an Israeli invasion eventually could lead to another conflict in the Middle East -- "if not immediately, then a short time later."
This seems to be the prevailing view here. But some analysts nevertheless feel that, just as a major breakthrough in peace negotiations probably cannot be expected before the first of the new year, so a major military change also is unlikely before then.