There were no triumphal drum rolls or trumpet fanfares today as Palestine Liberation Organization Chairman Yasser Arafat made his final passage through the city that has been his home in exile for 11 years.

Instead, his sad convoy along the bomb-cratered streets of West Beirut was accompanied only by the mournful wail of sirens, the odd shouts of encouragement from passers-by on the sidewalk, and the desultory rattling salute of machine guns fired into the muggy summer air.

With the majority of his PLO forces already evacuated from the city that has been their capital-in-exile, it was finally time for the 53-year-old bearded PLO leader to say goodbye and put the best face possible on his latest forced exile--his second from an Arab country in 12 years.

Always one to find signs of victory amid seeming defeat, Arafat left the city where his forces had been besieged by an invading Israeli Army for 10 weeks, proclaiming the battle "a symbol of heroic victories" for the Palestinians as well as Beirut's Moslems who had endured the war with them. It is a victory, he has proclaimed, that heralds "a new dawn" in the Arab world.

His rhetoric notwithstanding, and whatever way the PLO chairman chose to add up the political pluses and military minuses of the PLO's survival of the battle of Beirut, anyone who watched his forlorn departure from the city today could say that a major page in Middle East history had been turned.

The dream of a Palestinian nation that he has nurtured and fought for will undoubtedly live on, perhaps stronger than ever given the sense of pride felt by Palestinians as a result of their belief that they stood up to Israel's superior Army longer than any Arab nation. Arafat, always one of the wiliest of the Arab world's politicians, is also likely to emerge with his stature among fellow Arab leaders enhanced.

But the battleground of the PLO's continuing struggle is now expected to be diplomatic rather than military. The disarming of the PLO evacuees on arrival in Arab countries that have given them sanctuary makes clear that military options, always more symbolic than real, are no longer a practical policy.

Although the PLO has come out of the confrontation with Israel with its basic organization intact and with its leaders and key cadres alive, the PLO has been uprooted from a strategic base on the periphery of the area where it seeks to create a state of Palestine. All its men, and leaders, are scattered in a new diaspora that will erode the new-found unity and identity forged in their common struggle in Beirut.

Such assessments, being made by Western and Arab analysts alike here in the wake of the U.S.-mediated withdrawal of the PLO from Beirut, are not ones that are publicly acknowledged by Arafat and his fellow PLO leaders in these melancholy days.

Exile and dispersal, they argue, are not new to Palestinians. They will survive, they say, as they survived being uprooted from their homeland in Palestine in 1948 when the state of Israel was created. They will endure as they did after Israel occupied the West Bank of the Jordan River and the Gaza Strip on the edge of the Sinai after the 1967 Arab-Israeli war.

Arafat and the PLO are confident they will not only survive but flourish again as they did after their humiliating defeat at the hands of Jordan's King Hussein in 1970 in a month recorded in the history of Palestinians as "Black September."

It is of such a past of defeat and humiliation that the PLO has been forged. To understand this is to understand why Arafat, who has been struggling for a Palestinian state since his student days in Cairo in the 1950s, can claim to see victory even in the most obvious defeat.

The painful travail of his departure from Beirut today was no doubt made easier by the knowledge that he has gone through as much, or worse, before. In his pursuit of a unified Palestinian movement, he has endured jails in numerous Arab countries, as well as assassination attempts.

Despite the mob scene that forced the cancellation of a small departure ceremony, Arafat marched off toward the gates of the port with an air of stoic dignity, smiling serenely, as he said his final goodbyes to the West Beirut Moslem leaders who had rallied to his side.

For all the official rhetoric of the occasion there was no triumph in Arafat's departure. Instead there was a mood of tragedy and pathos around the port where his friends and allies had gathered.

"These people are saying goodbye to their hopes," said one West European diplomat who declined to give his name. "They are all putting on a brave face, but they know deep down that they are back to square one."

In his final hours in Lebanon, Arafat expressed bitterness toward his fellow Arab leaders. Alluding to the fact that no Arab nation had rallied to help his movement struggle against Israel in its moment of greatest need, Arafat told a group of students that the snows of Lebanon's Mt. Hermon were "warmer than the hearts of some Arab regimes."

The statement summed up the Palestinians' deep resentment that though their cause has always been used as a political football by fellow Arabs, in the end these Arabs were as happy as the Israelis to see the PLO humbled and weakened. With their cadres now spread among eight Arab nations ranging from Iraq to Algeria, PLO officials have made little secret that they hope their influence in their new homes will soon have a political effect on the regimes that abandoned them.

"The volcano has started to erupt in Beirut," Arafat told the group of Lebanese students, "and the trembling of the earth will be felt in many other places." With a large part of his organization in Syria under the tight control of President Hafez Assad, with others scattered amid such dictatorships as those in Iraq and South Yemen, it remains to be seen just how effective Arafat will be in making his voice heard in Arab and world councils from his planned new base in Tunis.