This war-ravaged country went through a revival of violence last week that again exposed the fragility of coexistence between Lebanon's Moslems and Christians.

The occasion was the anniversary of the violent clashes between the two communities that sparked 18 months of civil war and destroyed the countrys' political life.

The setting was Ain Rummaneh, a Christian suburb where the Lebanese civil war began just three years ago.

And as has become customary, there was much destruction and at least 50 victims to add to the roughly 60,000 persons killed in the civil war and its aftermath.

This latest outburst of killing was sparked by an incident involving an Ain Rumaneh man named Salim Hamoud.

During a visit to the neighboring - and rival - Moslem suburb of Shiyah he was pushed around, slapped and bitten on the shoulder in a disagreement with some fellow dealers in arms, hashish, cocaine and whatever else is for sale in Lebanon's free wheeling underworld.

The incident was neither more or less trifling than those which touched off some previous rounds of violence here. One, for example, stemmed from a disputed pinball machine game.

Nor was it particularly surprising.

There are more guns than people in this Connecticut-sized country, now condemned to coexist with seven armies: its own fledgling national outfit, the Palestinians, rightwing Christians, leftwing Moslems, the mostly Syrian 30,000-man Arab deterrent force, the growing U.N. force - now 2,000-strong - and the Israelis.

For days before the incident, Beirut had buzzed with rumors that the anniversary would be violent. The law school chancellor at the Catholic University on the Christian side of this divided city, for example, published a notice for the week dropping the usual mandatory attendance requirement and ordering lectures on nonessential subjects.

Once the fighting between Shiyah and Ain Rummaneh got going in a massive way, the Syrians intervened - at the nominal request of Lebanese President Elias Sarkis.

The Palestinians, who traditionally help the Moslems of Shiyah, stopped fighting. But not the Beirut area Christians. They had humiliated the Syrians in February - killing more than 80 of them - in shooting stemming from an incident at a Lebanese army barracks.

This time the Syrians took their revenge, using cannon, rockets and other heavy arms. The death toll at Ain Rummaneh was 37. All but two of the victims were civilans.

In the process, the Palestinians and Syrians scored a few points at the expense of the Beirut Christians.

Following their letdown when the Israelis stopped at the Litani River - rather than sweeping all the way north to Beirut - the Christian war-lords had kept that wild dream alive and adopted a new strategy designed to weaken their arch enemies, the Palestinians.

The Christians hoped to turn the Moslem half of the country against the Palestinians - the Shia sect because they had suffered at the hands of the Palestinians in the south and had their homes destroyed in the Israeli retaliatory invasion and the Sunni because the Palestinians were a cause of anarchy and disorder.

TR 4

The tactic backfired, and the Palestinians emerged as the principal beneficiaries - at least temporarily - of the strife that had rapidly changed from pitting Christians against them to a straight Christian-Syrian conflict.

In the process, the Palestinians solidified claims to being the Lebanese Moslems' best protectors.

The Palestinians also deflected Lebanese resentment for their anarchial behavior in the South, which Israel had invoked to justify its invasion.

And the Christian warloards, principally former president Camille Chamoun and his National Liberal Party, and Pierre Gemayel's Phalangists, were foiled in their efforts to maneuver the Syrians into fighting the palestinians.

Former president Suleiman Franjieh, nominally the thirrd Christian warlord, has preferred to maintain his longstanding ties with Syria and has limited himself to running the northern Christian stronghold from his hometown of Zhgorta.

Once again the Christians are talking about splitting the country, but any partition is tied to the apparently far-off possibility that the Israelis would mount a major military operation in the Beirut area.

Christian extremists seem willfully ignorant that criticism of the southern Lebanese invasion in Israel itself questionable.

"We Christians are becoming increasingly paranoid," one of their finest political analysts said. "We want to replace the Syrians with the United nations because we think anything is better than an Arab army of occupation. Basically, we want a Christian country and Syria is not about to allow that."

"I am more pessimistic now than even in the worst moments of the civil war," he said."Then we thought the the Syrians would come and stop the killing and madness and then we thought a new president could start afresh to repair the errors. Sarkis replaced Suleiman Franjieh and the Syrians have proved as incapable as anyone else".

Worrying out loud, he said: "If the Christians continue to escalate - and the Israelis don't do more than providing ammunition and a few advisors - we are headed straight for suicide."

"And if the Israelis do what we want them to," he concluded, "it would be slow motion suicide for us - and all Lebanon."

"During the civil war I saw the light at the end of the tunnel, but no longer," he said.