Jerusalem — After living through the era of flamboyant, unpredictable ex-Defense Minister Ariel Sharon, who led them through the Lebanon war, Israelis are beginning to assess the five-month performance of his successor, Moshe Arens.
This performance is critical because Mr. Arens will have to guide Israel's tortuous withdrawal from Lebanon in the face of Syrian obstinacy, as well as future policy on the Israeli-occupied West Bank.
It gains in importance as the increasing withdrawal of Prime Minister Menachem Begin from active political life - in the wake of his wife's death and the disappointing aftermath of the war in Lebanon - gives rise to speculation about his successor.
And Mr. Arens is being closely watched by the United States, where he just concluded a successful stint as Israel's ambassador, because he has played a key role in improving sagging US-Israeli relations.
There is no question that the slight, bespectacled, low-key but firm Mr. Arens is vastly different in style from his loud, rough-talking, corpulent predecessor, who was nicknamed the ''Bulldozer.'' ''The main advantage of Arens is that he is not Sharon,'' wrote an Israeli journalist.
Given Mr. Sharon's brilliant but erratic nature, such differences of style can have a large impact on policy. More complex is the issue of differences in substance.
Both men are hawks. But Mr. Sharon, brought up in a Labor Party family, was described by a knowledgeable military correspondent as a ''pragmatist and a careerist,'' who might conceivably have been ''capable of supporting a Palestinian state'' if he thought this was in Israel's interest. In fact, Mr. Sharon once asked a left-wing Israeli politician to arrange a meeting with Palestine Liberation Organization chairman Yasser Arafat (which never came off).
''With Moshe Arens, this would be impossible,'' noted military writer Eitan Haber of the conservative daily Yedioth Aharanoth.
Mr. Arens, born in Lithuania and raised in the US, has strong ideological views formed by childhood membership in the Revisionist Zionist movement, of which Menachem Begin was a key leader. He served during Israel's independence war in Mr. Begin's underground anti-British terror group, the Irgun, and has been active since in Mr. Begin's Herut Party, which believes firmly in Israel's right to the occupied West Bank and Gaza Strip areas.
Arens turned down an earlier request by Begin that he become defense minister , because he could not accept the peace treaty with Egypt (which he now accepts as policy). Begin ultimately appointed Ariel Sharon.
Writes Mr. Haber, ''Arens . . . is a hawk in his views but wears silk gloves on his nails. He is so pleasant, dry, and boring, yet so human and fair, that it is difficult to fight him and it is hard to find someone who would say a bad word about him.''
And yet, the differences of style between the two men have so far produced a much more cautious and pragmatic policy under Arens, an aeronautical engineer and technocrat by training.
Sharon did not hide his master plan to reshape the Mideast through military force by driving the Palestinians out of Lebanon and ultimately into Jordan, where he predicted they would finally set up their state.
Informed sources say Arens is much more a man of the status quo. ''Arens has no concept that Israel should use military authority to shape a new Mideast border,'' says an Israeli source close to the defense minister.
Arens placed highest priority on repairing relations with the US, which Sharon openly accused of preventing Israel from securing a peace treaty with Lebanon.
According to a close associate, Arens's strategic view of the region envisions a strong American and minimal Soviet role. ''For Arens, we need the US and have to have cooperation with it,'' said the associate. Arens also realized that good relations with the US were necessary to speed financing of a project dear to him, the Israeli-built Lavie fighter plane.
Given these concerns, Arens was willing to accept a US-mediated accord with Lebanon, which fell far short of what Sharon had envisioned.
Faced with a very difficult Lebanon situation created by others, Arens has now decided to cut losses by redeploying Israeli troops to more compact lines.
Mr. Arens also proved extremely cool during a high alert when Syrian spring training exercises gave rise to speculation about their intentions. An Israeli analyst noted, ''There was the right precaution without panic. He sent very exact messages to the Syrians and he was understood well.''
On the West Bank issue, Arens's ideology appears to have clashed somewhat with his tactical flexibility. He has endorsed the rebuilding of a Jewish quarter in the center of the volatile West Bank Arab city of Hebron, holy to both Arabs and Jews. Many observers believe such a move guarantees Arab-Jewish violence in a town where the murder of a Jewish settler was just met by Jewish destruction of the Arab marketplace. But Arens has said he cannot accept such a view.
A key test for the defense minister will be whether he can fulfill his pledge to see that the law is enforced on the West Bank without discrimination against Arab or Jew.
With Prime Minister Begin increasingly withdrawing from the political scene, speculation has begun about Arens's chances as a successor. Even some Labor Party politicians are saying privately that if the governing Likud Party seems like a winner, they would prefer Arens to any alternative.
The defense minister himself has not added to the speculation. ''He knows better than to try to replace Begin,'' an insider said. '' 'Arik' Sharon didn't help his chances by saying publicly he wanted to be prime minister.''