On one Sabbath earlier this year, this normally calm city of 135,000 people just outside Tel Aviv turned into a battleground. Thousands of religious Jews, with the traditional beards and skullcaps, massed in front of a moviehouse, shouting such things as ''criminals,'' ''dogs, '' ''Nazis,'' and ''violators of the law of God.'' When nonobservant Jews tried to buy tickets, the religious threw rocks at them. An open brawl ensued. Scores were injured.
Week after week such demonstrations have continued. The Orthodox say they will not stop them until the law of God is honored and cinemas and cafes closed on the Sabbath - sundown on Friday to sundown on Saturday. The secular have been just as intransigent.
''It's Jewish Khomeini-ism,'' says Dan Ben Canaan, assistant to Petach Tikva's mayor, Dov Tavori. It was Mr. Tavori, a Labor Party member, who triggered the dispute by trying to end the Sabbath restrictions in town. ''We will not let the religious take the law into their own hand and tell us how we should act.''
The battle between observant Jews and less- or nonobservant Jews is growing sharper throughout Israel. The stakes are immense. The outcome will play a large role in determining not only the future shape of the country's society and democracy, but also its foreign policy. Religious Jews, after all, are leading the settlement drive on the West Bank, and secular Jews, the opposition to it.
The division is also important in the Diaspora, the world Jewish community outside Israel. Diaspora leaders worry whether the American Jewish community can retain its cohesiveness and effectiveness if it is being torn from within. Divisive issues are wide ranging - from whether to accept public funds for religious education to what standards should apply to conversions to the Jewish faith.
''The split is affecting Jewish life everywhere,'' says Roland Gittelsohn, rabbi emeritus of Temple Israel, a Reform congregation in Brookline, Mass. ''When I became a rabbi 48 years ago here, I had lots of Orthodox friends. Today , there's not a single one with whom I can sit down at the same table.'' Emancipation posed a crisis for Judaism
The intensity of the struggle and the specific issues between the observant and less observant may be new, but the fundamental question being debated is not.
It dates from the French Revolution of 1789, which led to Jews in the West gaining equal rights with non-Jews. By breaking down the barriers of church and state that kept Jews apart from their neighbors, the emancipation posed a crisis for Judaism - how to adjust one's religious loyalty, which carries with it separation from non-Jews, to Jews' new political and social equality; how to adjust to the new rational, intellectual climate.
Many 19th-century Jews solved the problem either by converting to Christianity or by abandoning religion altogether. Others decided to adapt Judaism by modernizing it and eliminating whatever external differences might hamper the close relations of Jews with their neighbors. They also tried to remove or play down whatever tended to call into question their loyalty to the country in which they lived.
Jewish laws such as the dietary rules and Sabbath restrictions on travel and work were discarded. Religious services were patterned after Christian services, with the sexes no longer segregated, and music and responsive reading added. The idea of completely dropping Hebrew in favor of the vernacular was even considered. This brand of Judaism, labeled Reform, began in Germany in the early 1800s and was brought to the United States by German Jewish immigrants.
The fundamental difference between the Reform and Orthodox branches lies in their approaches to the Torah. For the Orthodox, these five books of Moses - as illuminated by the oral tradition now contained in the Talmud - are God's revealed word; they can be studied closely and discussed but must be followed as the inviolable law of God. For most Reform Jews, the texts represent the God-inspired words of the early Hebrews; they are to be respected as unique insights but must be adapted to fit each new modern era. Orthodox are minority among US Jews
Much of modern Jewish history lies across this fault line. Until recently, Reform or Reform-inspired brands of Judaism had the initiative in competition with Orthodoxy.
In the US, Reform Judaism together with Conservative Judaism - which accepts change but values continuity with the Jewish past and the essence of Jewish law - dominate Jewish life. Orthodox Judaism, which holds unswervingly to traditional teachings, remains in the minority.
''For a long time, we were considered namby-pambies, antiques,'' says Moshe Sherer, president of the American branch of the Orthodox organization, Agudath Israel. ''We weren't taken into account in group decisions.''
Adds Reform Rabbi Gittelsohn: ''We just assumed Orthodoxy was on its way out.''
In Israel, no formal Reform movement took root. Many of the early Zionists rejected religion outright, substituting a faith in work and socialism. True to that vision, when Israel was created in 1948, it was fashioned largely as a secular, Western democracy.
Orthodox Jews were on the periphery of Israel's founding. In numbers, they were and remain only about one-fifth of the Israeli Jewish population. Though they gained some influence through their political parties, which joined government coalitions, the Orthodox were never at the forefront forging the new state.
''Twenty years ago, a religious kid in Israel had the feeling he was inferior , that he didn't participate in Israeli life,'' recalls Avi Ravitzky, a philosophy professor at Hebrew University in Jerusalem and an observant Jew.
Today, this inferiority complex has vanished. Orthodoxy is experiencing a renaissance, both in the Diaspora and in Israel. It is growing not so much in numbers, but in self-confidence and aggressiveness.
In Israel, the break came in 1967 with the six-day Arab-Israeli war in which Israel ended up occupying the West Bank and Gaza Strip. Some Orthodox Israelis, finding the Jewish state in possession of what they saw as the old biblical lands of Judea and Samaria (the West Bank), began using religious justifications to settle there. No longer were the socialist Zionists the pioneers.
''After 1967, the religious suddenly had a psychological opening to become leaders,'' Professor Ravitzky says. ''We could go to the (West Bank) mountains and be the new super Jew.'' Begin's election boosted Israeli Orthodoxy
Orthodoxy's influence became even more pronounced after the right-wing Likud coalition's Menachem Begin came to power in 1977.
''Begin let the Orthodoxy move to center stage,'' explains Janet Aviodad, a sociologist at Jerusalem's Van Leer Institute who specializes in the Orthodoxy and is an activist in Israel's dovish Peace Now movement. ''His interests coincided with their interests, so he used them, and they used him.''
The alliance led to an increase of Jewish settlement on the occupied West Bank. It also meant increased spending on religious schools and greater public observance of the Sabbath - for instance, by stopping Israel's national airline, El Al, from flying on Saturdays. Mr. Begin even introduced a bill in parliament to redefine the term ''Jew,'' following the strictest Orthodox interpretation. This issue resurfaced during this year's election campaign and the political maneuvering that followed.
Meanwhile, Orthodoxy drew on its renaissance in Israel to become stronger in the Diaspora, too.
In the US, Orthodox Jews remain only about 10 percent of the American Jewish population, according to Harvard University sociologist Nathan Glazer. But, he says, Orthodoxy includes an increasing proportion of young Jews, which was not the case in the past. Professor Glazer and other sociologists attribute this change to a search found throughout America for religious values.
''There's a rising tide of militancy in Orthodoxy,'' says Arthur Levine, president of the United Synagogues of America, the national coordinating organization of Conservative synagogues. ''Religiously, it translates into greater strictness. Politically, it translates into greater self-confidence.''
This new militancy has strained cooperation between the Orthodox and non-Orthodox. The Orthodox have never recognized the theological legitimacy of the other brands of Judaism, and soon they may no longer work with Reform or Conservative Jews on social and political issues.
''They are becoming more right wing,'' says Milton Himmelfarb, a sociologist with the American Jewish Committee, ''and that is causing tension because most Jews are traditionally liberal.''
Reform Judaism is responding to the Orthodox challenge by becoming more sensitive to tradition. Specifically, it is increasing the use of Hebrew in its synagogues and restoring other traditional practices.
''In its desire to eliminate everything that smacked of non-reason, early Reform went too far,'' says Rabbi Alexander Schindler, president of the Union of American Hebrew Congregations, the Reform association of synagogues. ''Now we're more willing to accept the mystical, emotional aspects of Judaism.''
Reform is also counterattacking by strengthening its international influence outside its American stronghold. In Israel, it is lobbying to have its rabbis fully recognized as legitimate by the state. At present, marriages and other Jewish ceremonies conducted by non-Orthodox rabbis are not recognized in Israel.
Rabbi Schindler recalls how he told Prime Minister Begin that ''the gates of Auschwitz were open'' to all Jews, Orthodox and non-Orthodox, so surely ''the gates of Jerusalem must be open to all Jews.''
Rabbi Michael Williams of Paris's Rue Copernic Synagogue, the first Reform synagogue in France, adds that the exclusion is unwise: ''Only a minority of Jews are going to remain Orthodox. All the others who want to retain some contact with Judaism will have no place to go. They'll either drop it totally or become mad.'' In Israel, his prediction rings true. The anger of many nonreligious Jews is swelling. And the Petach Tikva battle has become a key test for the whole nation. The Labor Party majority on the municipal council is hoping to set a precedent that will keep open entertainment spots in cities throughout the country. Mayoral spokesman Dan Ben Canaan says the dispute involves the very soul of the Jewish state.
''The fanatics are trying to transform Israel into a religious dictatorship, prohibiting the freedom of the individual, just like in Iran,'' Ben Canaan says. ''We want to keep religion and state separate.''
The religious, of course, don't see the problem this way. They say violence against nonobservant Jews is committed by a few misguided youths. They also say they don't want rabbis to rule Israel but merely to create enough Jewish ''atmosphere'' so that Israel retains a true Jewish flavor.
''I'm not telling them what they must do inside their houses,'' says Rabbi Aharon Beifus of Petach Tikva. ''I'm just saying that outside in the streets, the Shabbat (Sabbath) must be guarded.''