Lebanon: PLO faces defeat on two fronts

The fighting in Lebanon has ended the initial military phase of what Israeli planners have long wanted to do:

To seal off Israel's border with Lebanon and make it as ''Palestinian-proof'' as the Jewish state's three other borders with Arab lands - those with Egypt, Jordan, and Syria.

With that operation successfully in hand, the Israelis can be expected to intensify their efforts to make their hold on the West Bank and Gaza more impregnable than ever. The government of Prime Minister Menachem Begin will feel in a stronger position than ever now to resist any territorial compromise with the Palestinians.

This, in turn, raises the question of whether all hope is now dashed of any meaningful discussion of Palestinian autonomy - one of the key aims of the Reagan administration's Middle East policy.

Even before Egypt's peace treaty with Israel, the governments of Egypt, Jordan, and Syria learned that they risked Israel's ruthless mailed fist if they allowed any Palestinian operations against Israel from their territory. The result: There were virtually no such operations.

Only from across its border with Lebanon did Israel continue to face armed Palestinian incursion or attack. This was partly because Lebanon had no government effective enough to rein in local Palestinians and prevent their using Lebanon as a base against Israel.

It was also because of international pressure intermittently exercised to spare the Palestinians the full fury of Israel's military might. This resulted in the Palestinians having some measure of sanctuary in Lebanon, not only for armed operations against Israel, but also for organizing terrorist operations in Europe and other regions.

Israel's use of its military sledgehammer in Lebanon this past week is intended to end that. The Israeli Army occupies the southern half of Lebanon, from which the Palestine Liberation Organization (PLO) has operated. Israeli troops are almost at the gates of Beirut and are near to controlling the highway from Damascus to the Lebanese capital.

There they are likely to stay while they do their best to reshape the political (if not geographical) map of Lebanon.

The Israeli announcement that they had achieved their military objectives June 11 contained a significant reference to a ''free and independent Lebanon.'' And an article in the Boston Globe by Shlomo Avineri, former director-general of the Israeli Ministry of Foreign Affairs - and no last-ditch hard-liner - said of Lebanon:

''A cantonal system may be advocated. . . . Or - if the call for this is strong enough - perhaps a Christian Lebanon should be carved out of the Christian areas, with the Muslim areas ceded to Syria.''

If the armed Palestinians in Lebanon have seemed the most immediate threat to Israel, it was not because of numbers. There are roughly 3.5 million Palestinians altogether, and of the just under 2 million living outside historical Palestine, only about 300,000 are in Lebanon.

With the armed Palestinians in Lebanon apparently being brought under control , Israel will find its biggest challenge coming from Palestinians still in historical Palestine. Some 500,000 live there as citizens of Israel. The 1.25 million others have been under Israeli military occupation on the West Bank and in Gaza since the 1967 Arab-Israel war.

Israel's Arab citizens have been relatively passive. But the Begin government's increasingly repressive policies in the occupied territories have produced potentially explosive situations this year both on the West Bank and in Gaza.

Israel's nearly nine-year-long negotiated return of Sinai (not claimed as part of Old Testament Israel or Eretz Israel) was used as a virtual smoke screen to proceed with incorporation of the West Bank and Gaza into Israel.

It has been a long and relentless litany: annexation of Arab east Jerusalem; the gradual spreading of Jewish settlements on the West Bank; whittling away of water rights of West Bank Arabs; acquiescence in the extremist activities of the Gush Emunim organization; cat-and-mouse pressures on Bir Zeit and other West Bank universities; the political emasculation of elected West Bank mayors; tolerance of vigilante operations against Arabs by Jewish hard-line settlers; and an overall pattern bordering on terrorism clearly aimed at producing Palestinian flight from the West Bank to elsewhere in the Arab world.

The Israelis saw local resistance to this pattern as inspired from PLO bases in Lebanon. Their hope will be that this influence has been neutralized, if not removed, by last week's military operations in Lebanon. They are likely to step up the process of digesting the West Bank and Gaza.

They will want to accelerate a fait accompli before the United States and the rest of the international community resume pressures to compromise with the Palestinians on self-determination. To such pressures, Prime Minister Begin and his hard-line team will offer last-ditch resistance.

To them, yielding territory to the Palestinians would mean beginning to reverse nearly a century of history. They see it as leading to the eventual demolition of the state of Israel.

Do the Israelis have any compensation to offer the Palestinians for the latter's continued exclusion from control of any part of Palestine?

Yes, it is the recognition as a Palestinian state of the present kingdom of Jordan, where 1.1 million Palestinians already constitute more than half the total population. Any such proposal is unacceptable to Jordan's King Hussein, who is naturally alarmed at its implications.