From the troubled region along Lebanon's border with Israel to Beirut's embattled Palestinian refugee camps to the shell-scarred airport, Lebanon's Shiite Moslem community in recent weeks has lived up to its new role as one of the most forceful movers of events in this beleaguered nation.

Once a community that considered itself disregarded, deprived and disinherited, the Shiites, through mainstream movements or more radical and undisciplined offshoots, are now exercising their political will on this shattered country as never before. Through the growing influence of the large Shiite Amal movement, its leader Nabih Berri has carved out for himself a central role in Lebanon's odd mix of traditional and feudal leaderships.

Since the first of the year, Amal militiamen have seized control of West Beirut, carried out a major harassment campaign against departing Israeli troops and fought with Palestinian guerrillas in bloody battles around Beirut's refugee camps. In the past two days, Shiite militants carried out a spectacular hijacking, although their link to Amal is not clear.

While the Shiites' role in Lebanon's politics has been growing steadily, it is the bitterly fought battles in the refugee camps, to which the hijacking appears connected, that have drawn the greatest attention to their emergence.

The departure of the Israelis from the south, the traditional homeland of many of Lebanon's Shiites, was widely claimed by Amal as its own victory and it soon plunged into a bitter fight against Palestinians in the camps outside Beirut to prevent the reemergence of a guerrilla presence in the south that could become a lightning rod for new Israeli incursions.

Lebanese Shiites believe that they have paid a heavy price for the Palestinians over the past few years, one unequaled by all the money donated to the guerrillas by oil-rich governments.

Angered by the Arabs' failure to take a stand or help when Beirut was under siege and heavy bombardmrent by Israeli troops in 1982, the Shiites now feel even more embittered by the Arabs' compassion for Palestinians in Lebanon, whose activities are strictly limited elsewhere.

"Why do you ask us to treat the Palestinians differently from the way you are treating them?" a lengthy communique issued by the hijackers of the Jordanian plane this morning said. The statement addressed the Arabs as liars and accused them of hypocrisy and holding double standards.

Blowing up the Royal Jordanian Airlines Boeing 727 today after freeing its passengers and crew underlined the Shiites' wrath at the Arab world.

It was the first time hijackers had destroyed an airliner in the Middle East since four aircraft were blown up by Palestinians in 1970. In December 1968, Israeli airborne units blew up 13 Lebanese Middle East Airlines planes at the Beirut airport in retaliation for a Palestinian attack on an El Al plane.

Amal, Arabic for "hope," was founded in 1974 by the visionary and charismatic spiritual leader, Imam Musa Sadr. It attracted followers from the impoverished and underdeveloped rural regions of the Bekaa and south Lebanon.

The Shiites had been growing in numbers significantly, but they had been all but ignored by the Sunni Moslems and Christians who controlled Lebanon's politics.

The tall, blue-eyed and articulate Sadr, of Lebanese-origin but raised and educated in the Iranian religious center of Qom, sought to instill in the despondent and passive Shiite villagers a sense of identity, purpose and belonging.

Before Amal gathered momentum as the Shiites' vehicle for identification and self-assertion, communist and Palestinian groups had found in that disgruntled community a fertile ground for recruitment, a situation that continued even after the emergence of Amal.

Then, in 1978, Imam Sadr vanished mysteriously while on a visit to Libya, prompting a series of hijackings by outraged Shiite activists demanding to know the fate of the missing imam and to focus attention on the plight of his community. With the outbreak of the religious revolution in Iran, Lebanon's Shiites were motivated to try to better their lot.

Many Shiites are convinced that Palestinians somehow had a hand in the Libyan-engineered abduction because Sadr had become too outspoken about the need for southerners to concentrate on their future as Lebanese and not get drawn in to the Palestinian cause. Others believe his abduction was linked to his acceptance of financial assistance from Libyan leader Muammar Qaddafi and refusal to continue fighting alongside the Palestinians.

Then, the presence of the guerrillas led the Israelis to launch their first major invasion of Lebanon in March of 1978, bringing misery and destruction to its predominantly Shiite southern villages and triggering a mass exodus of Lebanese refugees to the north. Alienated by predominantly Sunni Moslem Arab regimes, the Shiites of Lebanon turned inward. Relations with the Arab-backed Palestinian guerrilla movement soured, and violent clashes in and around Sidon before the Israeli invasion of 1982 underscored growing animosity between them.

With the virtual destruction of the Palestinian guerrilla movement in the south during the Israeli invasion and the general disruption of Lebanese politics, Amal and its new leader, Berri, a French-educated lawyer, began to assume a dominant role.

Amal moved to center stage in February last year, when, backed by Syria and other Moslem allies, it overran loyalist government troops, forcing the Army to split along Christian and Moslem lines.

Berri, who seized by force what he was not able to get by diplomacy from the government of Christian President Amin Gemayel, became minister of justice, power, hydraulic resources, reconstruction and state minister for south Lebanon.

Amal, although never a well-trained, disciplined or organized militia, became the largest among Moslem militias and became dominant in Beirut and in the south. The relatively moderate Amal line, was challenged by extremists in the Hezbollah (Party of God) movement and the Islamic Amal of Hussein Musawi, both with close links to Iran, but Berri held his ground.