On a balmy Saturday night two weeks ago, I found myself surrounded by a strange new Israel.

I was standing among 200,000 deliriously shouting Israeli citizens at a pro-war rally in the municipal plaza here. They were listening to Prime Minister Menachem Begin, arms waving and voice quivering, vow to deliver his country from terrorism.

The atmosphere was electric. Groups of young men in sandals and shorts punctuated the heavy air with rhythmic cries of "Begin! Begin!" and sometimes of "Begin the King! Begin the King!" The prime minister's hold over the crowd was so powerful that, had he called for a march on Lebanon, I had the feeling the tightly packed bodies would have headed north en masse.

Most of the Israelis I know did not go to the rally. They had seen this frenzy before, during Begin's reelection campaign, and they were disturbed. These demonstrations seemed to put on display an aggressive new culture, one that has caused shivers of apprehension among Israelis, as well as among Israel's allies throughout the world.

Later that evening I sat with some of my Israeli friends, watching the television replay on the late news. A few were supporters of the war in Lebanon, but all saw before them the symbol of an old order vanishing. Over and over I heard my friends say, "This is not the Israel I knew. These are not my people. This is not our Israel."

The Israelis I know, it should be understood, are not a cross section of the population. They are writers, doctors, diplomats, teachers, politicians. They are also Ashkenazis, which means that, like the overwhelming majority of American Jews, their origins and culture are European, chiefly central European. Most were born in Israel and have fought in all of its wars. Many have roots in the kibbutz movement and ties to the old ruling elite of the Labor Party.

The faces they saw on television were for the most part different from their own. They were the dark faces of Oriental Jews, products of the great wave of emigration, following Israeli independence in l948, from Morocco, Iran, Yemen and other points in the Arab world. These Jews, called Sephardis, are currently half of Israel's Jewish population.

At the time of the great Sephardi migration, Zionist leaders assumed that Jews in large numbers would in due course also arrive from the West and from Eastern Europe. Relatively few actually did. But almost all the Sephardis are now in Israel.

Israelis have long taken for granted that the Sephardis would, at some time and in some way, reshape the country's culture, but most assumed that the traditional Ashkenazi values would prevail. This war rally upset my friends by making clear that the time of the Sephardis had already arrived, and that it had taken a form they had not anticipated.

Many America Jews have made much the same observation, uncomfortably perceiving an Israel which in many ways seems to have departed from its original promise.

Scholars conventionally describe the Sephardi influence in Israel as "Orientalization." The rally contained some of its features: a strong attraction to overstatement, a ready disposition to emotional display. My friends said the demonstration might easily have taken place in Cairo or Algiers.

But Sephardi influence goes beyond such superficial concerns to the very purposes of Israel as a state. This is because the Sephardis grow out of a very different political, historical and territorial tradition from those who founded and long led Israel -- and they have formed an alliance with a man who also differs sharply from Israel's earlier leaders.

The Sephardi-Begin alliance is an apparent paradox. Menachem Begin is a Polish Jew, a quintessential product of Eastern Europe, with neither knowledge of nor interest in Oriental culture. How did he become the tribune of the Sephardi masses?

Israelis dismiss the idea of opportunism; whatever one thinks of Begin, he is no hypocrite. He is faithful today to the vision he held as a young Zionist leader in pre-war Poland. While he has been in search of a following, the Sephardis have been in search of a leader. They were culturally drawn to his flamboyance. But it is sheer coincidence that his idea of Zionism, too, now seems tailor- made to fit them.

Begin's philosophy has a specific name: revisionism. For more than half a century, it has been a strong competitor to mainstream Zionism, and the conflict between the two wings has more often than not been extremely unfriendly.

This had been so since the days of Vladimir Jabotinsky, revisionism's Russian-born founder and seminal thinker. If Jabotinsky could be characterized in a phrase, it would be "Jewish nationalist," but with the emphasis far more on "nationalist" than on "Jewish." Compared to other Zionist thinkers, Jabotinsky had little interest in the Jewish religion, in Jewish culture, in Jewish moral values.

He had one objective -- to set up a powerful Jewish nation-state -- and until his death in 1940 he gave it every ounce of his energy.

Jabotinsky rejected the tenets of mainstream Zionism, which favored lawful purchase and colonization of the land in Palestine, negotiation with the great powers to guarantee a Jewish homeland, cultivation of a new Jewish society based on the tenets of egalitarian socialism. He regarded their practice as diversions from the Zionist goal.

Jabotinsky wanted to establish a state, without delay, and he was ready and eager to achieve it by the force of Jewish arms.

Begin became a Jabotinsky disciple in the late 1920s, joining the new revisionist organization, Betar, in his native Brestlitovsk. Revisionism's friends today say Betar looked for guidance to the Masaryk-Benes regime seeking to create a free and democratic Czechoslovakia. Its critics compare its doctrines to the autocracy of Pilsudsky in Poland and Mussolini in Italy.

Both in some measures are right. Begin has been unwaveringly faithful to democratic procedures. But Betar indisputably had an authoritarian side. Its members wore brown shirts. It exhorted discipline, collective action, strong leadership. It trained with arms for the day when it could liberate Palestine "on both sides of the Jordan."

Menachem Begin, by wending his way eastward through Russia, arrived in Palestine in 1942. A year later, at age 30, he became commander of the revisionist underground organization called Irgun. In 1944, while the allies were still fighting the Germans in Europe, the Irgun launched its war of independence against Britain.

The mainstream Zionists, now led by David Ben-Gurion, were furious. They had not given up their reliance on diplomacy and, as revelations of the Holocaust unfolded, it became clear that world public opinion had swung around in favor of a Jewish state.

Indeed, by 1947, diplomacy did succeed, but surely Irgun's clandestine campaign of death and destruction -- which Begin refuses to call "terrorism" -- had much to do with Britain's decision to depart.

Independence, far from healing the breach, drove the two wings of Zionism farther apart. By now the battle was over the the configuration of the new state -- the issue that has left Zionist thought in angry disarray ever since.

Before leaving, the British partitioned Palestine into two parts, in one of which the Jews predominated, in the other the Arabs. A partitioned Palestine was less than the mainstream Zionists wanted, but they chose to accept it.

The revisionists declared they would not -- and indicated they would fight. The revisionists conceded no rights to the Arabs whatever over the land. They promised the Arabs equal treatment as individuals, but the overall hegemony in the country had to be Jewish.

The government of Israel -- which the mainstream Zionists had become -- was by now waging war with all the Arab states while looking warily over its shoulder at Begin's forces. In June 1948, Irgun men attempted to bring in a cargo of arms from a ship called the Altalena -- and to arm themselves with some of the weapons. Ben-Gurion rejected this challenge to the government's authority. With Begin aboard, the Israeli army opened fire, killing a good number of Irgun men and sinking the ship. Begin has never recovered from his sense of outrage over the affair.

After the war, Begin and revisionism went into eclipse. He was elected to parliament, but the party he had formed hardly seemed significant. On the eve of the Six-Day War in 1967, he joined a government of national unity. But he withdrew when the government endorsed U.N. Resolution 242, which established the principle that as part of an overall peace settlement, Israel would return the territories it won in the war.

In retrospect, it is clear that the acquisition of these territories was the turning point in Israeli political life. While they were in Arab hands, revisionist territorial aspirations were a dream, in which few Israelis showed much interest. But after the war, the territories were a reality, too dazzling, too intoxicating for the Israelis to ignore.

Shlomo Avineri, former director-general of the Israeli foreign ministry and one of the country's most respected political scientists, says that since 1967, Israel's entire political agenda had been transformed by these territories.

"When I was a student," he remarks, "what we debated in school were the questions that were internal to Zionism -- social justice, social democracy, the socialist models for our society, the organization of the kibbutzim. For my children, the debate is all external -- our claims to the West Bank, our attitudes towards the Palestinians, the reach of our boundaries. These are issues not so much of Zionism as of Israeli nationalism."

For the Labor Party, these are complex issues, requiring a painstaking reconciliation between the demands of security and traditional Zionist values. Labor has reconciled this conflict badly and thus appears bumbling, indecisive and weak.

Begin knows no such dilemma, no need to find a subtle balance. "The country is either ours or it is theirs," he has said. The Israeli army is the strongest in the region, and can settle whose the country is -- that is what Jabotinsky wanted and what revisionism is all about. With this platform, the strength of Begin's party has grown consistently since 1967, until now it dominates Israeli politics.

This domination has come about largely through a steady shift in the voting habits of the Sephardi community. In the early days, Sephardis supported Labor, the party which had brought them to Israel, but gratitude turned into resentment of the Ashkenazi ruling elite with its "cultural imperialism," and Begin was the beneficiary. In last year's Knesset election, nearly 70 percent of Begin's votes were from Sephardis.

Avineri attributes the Sephardi support of Begin's "right-wing populism" to the traditionalist and religious character of Oriental culture.

The Sephardis are indifferent to Ashkenazi talk of democracy, egalitarianism and socialism, concepts with which they have little familiarity. They respond to a strong leader like Begin who proclaims orthodoxy, certitude and faith.

Perhaps more important, they respond to Begin's identification of the enemy. For the Ashkenazis, shaped within the context of European anti-Semitism, the Arabs are a political inconvenience, a problem to be solved. To the Sephardis, who lived for centuries under Islamic domination, they are a detested foe with whom there are scores to settle. For them, Begin's message is not a distortion of the Zionist dream, a European creation they never really knew, but a call to strike back.

Over the protest of many of his followers, Begin returned the Sinai to the Arabs. But he made clear that even in exchange for peace, he has no more territory to cede. Furthermore, by referring constantly to Israel's current holdings as "Western Eretz Israel," he proclaims, if not the June 1948, Irevisionist vow to expand eastward, then at least his conviction that the Arabs hold this region at the sufferance of the Jewish state.

"Practically speaking, we probably can't have Israel on both sides of the Jordan, though we revisionists have never given up the notion," Dr. Eli Tavin remarks. Tavin grew up with Begin in Poland and fought with him in the Irgun in Palestine. A director at the Jabotinsky Institute in Tel Aviv, he now dedicates much of his time to keeping alive the memory of revisionism's founder.

"The Palestinains never had the rights they claimed over the lands," Tavin says. "But Israel, as a political matter, is unlikely to get all the space that rightfully belongs to it.

"Nonetheless, we must build a state with sufficient territory to assure our independence and our freedom of action again in the region. We need room to bring in millions more Jews. We must be strong enough to ensure our survival among 100 million Arabs. We think the war in Lebanon was necessary, and most Israelis support us in that. In fact, I think most of Israel is at last committed to the revisionist interpretation of Zionism."

Abba Eban, an Ashkenazi and a warhorse of the Labor Party, disagrees vigorously with Tavin's view. A former foreign minister and ambassador to the United States, Eban has long preached the necessity of reaching an accommodation with the Arabs. He contends that Israelis are too few in number and too dedicated to more humane objectives to count forever on dominating the Arabs by military force.

In behalf of the Labor Party, Eban argues that the revisionist reign will be short, and that most Israelis still favor territorial compromise in the interest of peace. "We would not have started the war in Lebanon," he says, "and do not believe in a Greater Israel." The very word "revisionist," he adds, acknowledges that "we are the norm." Before long, he argued, Israel will reaffirm at the polls the values of the Zionist mainstream.

More impartial than either Tavin or Eban, Avineri is convinced that the future lies, if not with the revisionists, then with something like the revisionists' vision. The Sephardis, with a higher birth rate than the Ashkenazis, will soon be a clear majority, he says, and the Labor Party, if it is to come to power again, must modify its doctrines to correspond with what they want.

What Avineri seems to be saying is that it is naive -- for the American government, for Western Jews, for friends of Israel anywhere -- to believe that Menachem Begin will give up any of the land that he calls "Eretz Israel," no matter what the prospects for peace.

As for his Sephardi followers, who take their political lessons from the millenia in which they lived uneasily with the Arabs in the Middle East, a peace based on compromise with their neighbors is of less interest than a peace based on domination.

Begin's ascendancy, Avineri says, symbolizes the Orientalization of Israeli politics, if not of Israel itself, and there is no sign that the trend will be reversed.