Beirut — Eight hundred United States marines Wednesday safeguarded the exit of hundreds of guerrillas with Yasser Arafat's Palestine Liberation Organization, an organization the American government does not recognize.
Wednesday's evacuation was the same as the first four evacuation days, with joy, tears, sorrow, and gunfire exploding throughout Muslim west Beirut.
The one new element to the pandemonium gripping the war-ravaged western half of the city was the novelty of American troops and the irony of their presence.
Six US ships came out of the pre-dawn mist. By the time the sky went from pink to blue, gray landing craft plunked the marines ashore at Beirut port.
Veteran American envoy Philip C. Habib, who negotiated for weeks to end the Israeli siege of west Beirut, stood by the quayside to welcome the men who would implement his peace plan. It was the first time in months the press or the Lebanese had seen the diplomat smiling.
About three hours after marching ashore in green mottled fatigues and carrying M-16 rifles, Echo company of the 8th battalion relieved the French Legionnaires in the port.
The Americans toured their new post with Col. Abu Zarad, commander of the Palestine Liberation Army. The PLA is one of the eight groups that make up the PLO.
The maroon-bereted Palestinian briefed both Capt. Kenneth McCabe and Lt. Col. Robert Johnston on the row of destroyed buildings he has commanded for four years.
The port district, where the Americans are deployed, was the scene of the bloodiest, most destructive battle during the 1975-76 civil war. Many of the marines surveyed the destruction wide-eyed - amazed to discover that the building shells were not leftovers of the Israeli-Palestinian war.
Asked what he thought about meeting his first PLO member, Colonel Johnston replied carefully.
''Well, I think I am pleased to see him because I think the fact that we are meeting even though I represent a multinational force and not exclusively the American forces is that it represents the possibility of some peaceful settlement to the problem of west Beirut.''
Colonel Zarad joked with Captain McCabe. McCabe complained it was hot. The Palestinian officer suggested he remove the flak jacket the Marines had been ordered to wear for fear of sniper fire.
''See, it is not dangerous here,'' Colonel Zarad said, unbuttoning his shirt to reveal a bare chest.
Since the civil war the port area has been a front line where the Palestinians and Lebanese leftists traded sniper and artillery fire with Christian militiamen regularly.
Before the French contingent of the tri-nation force arrived Saturday to begin the PLO evacuation, one would dare ride through the area only at top speed and on only the quietest of days.
Before 18 Lebanese Army trucks carted several hundred PLO guerrillas through the American lines, Colonel Zarad introduced Colonel Johnston to one of the youngest PLO fighters.
Six-year-old Yasser, decked out in fatigues and kiffiyah (the Arab headdress) , saluted the American and showed off his tiny, but real, AK-47 assault rifle. Bending to shake the boy's hand, the American smiled and returned to salute.
''We are teaching our chidren to struggle to take our land again,'' Colonel Zarad explained.
Nineteen-year-old Mohammed was not so polite about the marines' presence.
''I don't like to see them. They are my enemy - not the American people - the American soldiers and leaders,'' he said.
''If the Americans say stop, they (the Israelis) stop; if they say fight, they fight,'' the teen-ager said.
''They used American planes, bombs, rockets, . . .'' his voice trailed off.
Mohammed was studying engineering before he began fighting in the war, but he said he wasn't sure if he can continue his education in Syria.
The convoy of guerrillas arrived amid a hail of celebratory machine gun, grenade, and rocket fire. The marines generally watched impassively - protected first by Zarad's PLA men and then by Lebanese Army troops.
Hundreds of civilians trailed after the Palestinians, crying, chanting, and cheering. A Marine photographer accepted a badge from one guerrilla leaning over the side of the pickup truck. The badge had ''PLO'' emblazoned on the Palestinian flag.
Women held up a brightly painted sign saying ''Beirut will never forget.''