Beirut — For three days in mid-September they fought house to house, grudgingly giving ground as the Israelis advanced westward down the Corniche Mazraa from Barbir Hospital to the Abdel Nasser Mosque in west Beirut.
They fought with automatic wespons, rocket-propelled grenades, and Soviet-built T-34 tanks. Then, when they knew they were beat, they say they blew up their headquarters and 12 of their tanks to avoid having them go to the Israelis.
But the Israelis never came to disarm the leftist Lebanese Murabitoun guerrillas. It was the Lebanese army to which they turned over their guns and six surviving tanks. Now, for the first time in eight years, the Lebanese Army patrols the streets and alleys around Abdel Nasser Mosque and the streets are quiet.
''We have been fighting for eight years and we didn't get anything, so if you can fight politically it is better without destroying the houses,'' says one Murabitoun member.
The Murabitoun is said to have been the single largest private army in west Beirut with 1,500 men. Last week, Murabitoun leader Ibrahim Koleilat announced his support for the new Lebanese President Amin Gemayel.
Political observers say leaders of the leftist Lebanese militia may be maneuvering for a role in the new government, but they add that in light of their previous involvement as allies of the Palestine Liberation Organization and the Syrians they have no chance of playing a formal political role.
The Beirut that is emerging from the Israeli invasion, siege, and occuption is a Beirut tired of fighting and now apparently committed to rule by law, rather than the eight years of lawlessness this city is trying to walk away from.
As a result, the Murabitoun's loudest voice - the gun - has been silenced. It is expected the organization will rely now instead on its radio station, the Voice of Arab Lebanon, which broadcasts ''the truth'' daily from the second floor of the Abdel Nasser Mosque. The radio station was created to be the Muslim counter to the Christian Phalangist radio broadcasts in east Beirut.
In addition, the group had been constructing a television studio on the fifth floor of the mosque at the time of the Israeli thrust into west Beirut. Though the Israelis did not go after the Murabitoun itself, they did with their tanks manage to punch six holes in the mosque's minaret. Then, according to the Murabitoun, they entered the mosque, cut the wires on all their new television equipment, and took it away.
Almost every building in the area was scarred by automatic weapons fire. Down the road four Soviet-built tanks stood in a perfect line at the intersection where they were blown up by the Murabitoun.
The Murabitoun was meant by leftists here to become for the Sunni Muslims in Lebanon what Nabih Berri's Amal (Hope) is to the Shia Muslims or what the late Bashir Gemayel's Lebanese Forces is to the Maronites. It was meant to become an all-encompassing militia and political party for the Sunni Muslims.
But the Murabitoun failed to attract any significant following among the Sunnis, sources say, primarily because few Sunnis here are supporters of the political left.
Saeb Salam, former prime minister and elder Sunni Muslim statesman, calls the Murabitoun ''rogues of the street.'' He adds, ''These are stooges for outside political powers, they are thugs.''
The beginning of the end for the Murabitoun came in late August with the evacuation of the 14,000 Palestinian guerrillas and Syrian troops from Beirut. With their allies gone, the Murabitoun became vulnerable not only to the Israelis and Christian Phalange, but also to the Lebanese Army.
It was only a matter of time before the militia reversed its earlier rejection of President-elect Bashir Gemayel and began to disarm and turn over its positions to the Lebanese Army. Then the President-elect was assassinated and the Israelis drove into west Beirut.
The Murabitoun follows former Egyptian President Gamal Abdel Nasser's philosophy that the Arabs should organize and unite and be opposed to Israel. They have vowed to fight Israel whenever and whereever they can. This is one reason they were closely aligned with the PLO in Beirut.
Murabitoun members said Mr. Koleilat came out in support of President Amin Gemayel because of the President's statements that he would seek the withdrawal of Israeli troops from Lebanon and that he would not pursue a peace treaty with Israel without the support of the prime minister (who must be a Sunni Muslim) and the support of a public referendum on the issue.