The partial Israeli withdrawal in Lebanon in the wee hours of Sunday morning sparked the long-anticipated factional fighting between Christian and Druze Muslim militias in the Shouf mountains overlooking Beirut, in what many Lebanese feared was the opening stage of a new civil war.
Scenic mountain villages were shrouded in clouds of hazy smoke, accentuated by occasional flashes of fires, from the heavy barrages of artillery on Sunday and Monday that occasionally spilled over into the capital.
American efforts to bring about a truce have failed, although US troubleshooter Robert McFarlane was due back in Beirut Monday, after talks in Washington.
As a Western diplomat said Monday: ''Once again the sides are so polarized that what is acceptable to one side is totally unacceptable to the other.''
Dull, thundering explosions echoed through Beirut, with many shells landing in Christian-dominated east Beirut and on positions of the multinational force. Four marines and one Italian officer were injured in the fighting. Marine spokesman Bob Jordan said the marines fired back at militia positions in the Shouf twice when the 1,200-man US contingent came under fire at its encampment near Beirut's international airport.
The Lebanese Army did not move into the Shouf to fill the vacuum left by the Israelis, as they were expected to do. Thus there was no authority in the area to sort out rivals whose feud dates back more than a century.
Military sources claimed they were not given sufficient notice from the Israelis, and that there was none of the coordination the Israelis had promised. To show their anger, the Lebanese government announced that the US-orchestrated accord between Beirut and Jerusalem was ''frozen.''
But the timing was clear by Saturday, when Lebanese Prime Minister Shafik Wazzan spoke on nationwide television of ''this fateful day.'' The problem for the Army may have been that it was stretched thin by actions in the capital last week against Shiite Muslim militias. In effect, the Army was warned but unprepared, according to a Western military analyst.
On Sunday the Army took the strategic crossroads of Khalde on the Mediterranean coast to secure the road linking southern Lebanon with Beirut and to make it difficult for the Shouf war and militias in Beirut to connect: that could open the way for full-scale civil war. So far, the Shiite ''Amal'' militia has not joined forces with its Druze allies.
The fighting has been concentrated on three fronts, as Druze of the Progessive Socialist Party led by Walid Jumblatt have tried to push into Bhamdun , Souk al Garb, and along the coastal highway. Bhamdun is on the Beirut-Damascus highway, one of Lebanon's lifelines to the outside world. Souk al Garb is headquarters for the Christian Phalangist militia in the Aleih region.
Although there has been a flurry of meetings - in Beirut, Cyprus, Saudi Arabia, and Syria - to try to negotiate a truce, there has been little progress, Western envoys say. Many of those involved in the efforts to reach a truce are concerned that the fighting may only entrench the rivals.
A Western envoy said Lebanon had only a few weeks in which the Army could move in and sort out the ''mountain people'' before the whole US effort would collapse.
The Druze have pledged to fight the Army if it tries to deploy before a political reconciliation. The Druze and other Muslim groups say the Christian-led Army is too closely tied to the Christian Phalangist Party and its militias, and that deployment would give Christians an edge in subsequent negotiations. They have demanded peace talks first.
The implications for US efforts were explained by a leading Western diplomat: ''If the Army is not in unquestionable control of the Shouf and Aleih before the end of September, it would not make sense to pursue a (US) policy aimed at withdrawal of all (Israeli, Syrian, and Palestinian) foreign forces.''
The Israelis particularly would balk at further evacuation if the Lebanese Army is seen to be incapable of taking over and controlling strategic areas, envoys suggest.
The Shouf, Lebanon's heartland, has always been deemed the litmus test for the future of the troubled country, both politically and militarily. Without peace in the Shouf, the Lebanese government is not likely to regain sovereignty over the rest of Lebanon, in the view of envoys and the four multinational force countries.
The new fighting has been interpreted as a disaster for US policy in the region, particularly for the White House, which sent in its own envoy from the National Security Council, Robert McFarlane, to replace the State Department's Philip Habib. The new mediating team has convinced the Gemayel administation of the need for political reconciliation, an issue on which the government has been stalling. But so far the McFarlane team has not gotten the complex network of factions to agree on terms that would ease tension between the majority Muslims and minority Christians.