Will Lebanon be Israel's 'N. Ireland'?

With hopes for a political settlement in Lebanon fading, Israeli forces are maneuvering into position for what most analysts here say will be an assault on the Palestine Liberation Organization's last, densest stronghold in this country.

Though few observers believed the PLO could militarily survive this coming conflict, it also seemed doubtful Israel could both cause the PLO to disappear and then extricate itself from the quicksand of Lebanon.

A well-informed United Nations official who toured southern Lebanon and the hills east of Beirut June 24 said the Israeli Army was moving great amounts of armor and artillery toward the capital. The UN official saw the Israeli drive against Syrian-Palestinian positions in the Aley region, along the Beirut-Damascus highway, as a prelude to an assault on the capital. Taking the hills would be necessary, this official says, to neutralize potential cross fire if the Israeli Army charges into Palestinian parts of the city.

The departure from Lebanon of United States envoy Philip C. Habib, ostensibly to confer with Israeli leaders, was taken as a bad sign by the residents of western Beirut. Before leaving, Mr. Habib reportedly relayed a message to the PLO. This message had as its bottom line an ultimatum: After 11 days of plodding , indecisive negotiations, the PLO must decide whether to disarm unilaterally or face Israeli attack.

It seemed unlikely the PLO would knuckle under, given the fiery anti-Israeli feelings of most guerrillas.

Businessmen, diplomats, teachers, journalists, and others continued their exodus from west Beirut June 24. At the port of Junieh, north of the capital, Americans queued for passage on a naval transport bound for Cyprus.

The Lebanese ability to live with - indeed, to prosper at - ambiguity and half-settled affairs may eventually confound Israel. Even though Israeli soldiers have found friendly faces throughout the country, the amount of actual military aid Israel has received from Lebanese rightists in combating the PLO seems to have been minimal.

If Israel fights its way into PLO areas of Beirut and crushes the organization, it seems probable Israel will still face these problems:

* The Palestinians in Lebanon and other Arab countries will still work - via the PLO or some new organization - for establishment of a Palestinian zone in territory Israel holds.

* World and domestic opinion may eventually be turned by the destruction wrought by the Israeli invasion. Already critics in Israel and in the West are talking of atrocities committed by the invasion army against Palestinians and Lebanese, and most news coming out of territory Israel occupies is being censored.

* Israel may have to maintain an army of occupation in the country for years to come to secure areas in which Palestinians predominate and to make sure armed Palestinians do not infiltrate the country once again and turn it into a base of operations against Israel.

''I saw some Israeli officers today,'' a diplomat here told the Monitor, ''and I told them they had better get used to the country, that this could be their Northern Ireland for years to come.''

Estimates of current Israeli troop strength in Lebanon range from 60,000 to 100,000 men. Strategically, Israel, it seems, must choose whether to go after a quick, total military victory, chasing both the PLO and the Syrians out of Lebanon, or keep edging the other forces into northern and eastern Lebanon. The other alternative is to establish a permanent cease-fire supervised by a multinational force.

The first two options would require continual Israeli commitment of men and materiel. Many military observers here foresee a plodding, timorous campaign by the Israeli Army. Because of fears of Israeli casualties, the Israelis are applying astounding firepower against their foes before advancing. A UN official speaks of Israeli troops being held up at Jamhur in the mountains just east of Beirut, for three days while they waited for Israeli jets to disable one Syrian tank.

''They are playing it very cautious,'' this official says. ''They are deathly afraid of taking casualties and getting Israeli public opinion upset with them.''

The third strategic option open to Israel, a supervised cease-fire, would take Israeli willingness to disengage and withdraw from much of Lebanon before it has resoundingly crushed its enemies; otherwise, its enemies might be neither sincere enough or strong enough internally to maintain the peace.