Behind clashes in south Lebanon

The Middle East's most volatile confrontation line runs close to this quaint Lebanese Christian hamlet. The town overlooks the deep gorge formed by the elbow of the Litani River. The vista is breathtaking. But it was the scene of a new form of combat between Palestinian guerrillas and their Lebanese Christian foes.

Guerrillas are suspected here of having infiltrated from their perch atop the heights of Arnun, directly across the wide abyss separating the two sides, and of blowing up a Christian home.

As a result of the blast at dawn Feb. 11 and a subsequent Palestinian artillery barrage, four persons were killed and at least three wounded.

This incident has set the stage for a new escalation of fighting. It already has seen the Christian-dominated Lebanese forces commanded by maverick Maj. Saad Haddad shelling Palestinian targets within range of Deir Mimass, especially the medieval crusader fortress of Beaufort. Other attacks hit the Palestinians' exposed western flank, mainly the coastal town of Tyre.

One of the psychological reasons for Major Haddad's swift reaction undoubtedly was to prove to his beleaguered but loyal followers that he can provide an effective deterrent to the Palestinians.

If he cannot, Major Haddad believes the Israelis can and should.

The red-haired, temperamental Lebanese officer simultaneously reminded Israel's Prime Minister Menachem Begin of a pledge made last week that Israel will not let the Christians to overrun.

In the background of this new round of local fighting is a much broader development; the uncertain status of Syria's 30,000-man peace-keeping force stationed in Lebanon north of the Zaharani River.

President Hafez Assad of Syria served notice Feb. 4 that he was withdrawing his troops from the Beirut area and redeploying them in the Bekaa Valley and in other areas further south that could alter the fragile tactical balance with neighboring Israel.

Although he relieved the Lebanese government of President Elias Sarkis and other interested parties, including the United States and ironically Israel, too , by postponing the pullout -- a consequence of which would have been renewal of the Lebanese civil war -- the postponement evidently is still tantamount of destabilizing the status quo.

Otherwise, a high-level Lebanese government delegation would not have gone to Syria's capital, Damascus, to seek a more binding commitment from the Syrian leader.

Meanwhile, the Israelis have been busy speculating on the possible motives for the Palestinians to rekindle the southern Lebanon front.

Their first hunch was that the Soviet Union, which supplies arms to both Syria and the Palestine Liberation Organization (PLO), wants to create a credible distraction to its internationally condemned presence in Afghanistan. What better way than to heat up the Arab-Israeli conflict? Israeli military analysts, much as Yaakov Erez of the daily newspaper Maariv, stress the guerrillas' apparent mood of self-confidence now that the Lebanese coastal sector between Tyre and Sidon has been placed under their military control -- at Syria's initiative.

A logistical additive, according to Christian radio reports, is PLO receipt of "scores" of Soviet T-34 tanks. This equipment has been deployed in the coastal area.