NETIVOT, Israel – In the largest-ever planned march by opponents to Israel’s withdrawal from the Gaza Strip, tens of thousands of Jewish settlers yesterday confronted Israel’s police and army, which together mustered 20,000 officers and troops to disperse those gathered. A month before the planned evacuation of all Jewish settlers from Gaza and certain West Bank settlements, the government and demonstrators accused each other of violating democratic principles.

In an unprecedented move, police prevented protesters from gathering in this southern town about 15 miles from Gaza. Settler supporters said the action violated their freedom of movement and right to free assembly. But in a temporary ruling yesterday, the Israeli Supreme Court said that the violation of a law by demonstrators trumps their democratic rights.

“This is an illegal and dictatorial act,” a demonstration organizer, Eliezer Hisdai, told The New York Sun, as thousands poured into an area surrounding the tomb of the late rabbi Baba Sally, whom many in the settler settler movement revere. “Can’t we demonstrate?” Mr. Hisday said. “Can’t we have one at least one moment of steam-letting?”

In a tactical victory for supporters of the settlers, Internal Security Minister Gideon Ezra last night said the police would allow demonstrators to sleep over at nearby Kfar Maimon. They would not be allowed to advance toward Gaza, he said. After protesters’ speeches and prayers ended, the marchers moved to Kfar Maimon, where an advance team had prepared a tent city for the overnight stay. They hoped to enter the main cluster of Gaza Jewish settlements, known as Gush Katif, which yesterday was declared a closed military zone by the army.

A former aide to – but current opponent of – Prime Minister Sharon, Mr. Hisdai said that the police actions might lead to even more violence by young demonstrators. “I am not sure we can control their anger,” he said.

“They lied to us,” a Knesset member, Yitzhak Levy of the United Religious Party, which represents many constituents in Gaza and West Bank settlements, told the Sun. Police reneged on a promise to allow the demonstration, he said. “We do not want to fight against the army,” he said.

Government spokesmen and women said that defying the security forces was an undemocratic act. “They falsely use the language of democracy,” Justice Minister Zipi Livni told Israel Radio in reference to the settlers. The settlers’ intention to violate a ban on entering Gaza, imposed earlier this week, she said, justified the authorities’ actions. According to a poll conducted by Channel 1 Television yesterday, 62% of Israelis believe that the settlers’ attempts to prevent the government’s disengagement plan are “illegitimate.”

Yesterday’s march was widely seen as a dress rehearsal for the evacuation of all Jewish settlements in the Gaza Strip, as well as several in the North West Bank, scheduled for August 15. The plan has divided Israeli society along ideological lines. The Israeli press yesterday pointed to the example of an army captain and Gush Katif resident, Assaf Yemini. Some of the officer’s higher-ups told him that he would be forgiven for relinquishing his post commanding a company in the elite Golani force, which has been charged with confronting settlers. Captain Yemini held on. In skirmishes along police barricades, settlers called him a “traitor,” even some who knew him from childhood.

Demonstrators sported orange ribbons, orange hats, orange T-shirts bearing messages such as “With Love We Will Beat Separation,” and other orange accessories. Wearing the color in solidarity with the orange banner of Gush Katif has become a political statement this summer. The mass-circulation daily Yediot Achronot yesterday reported that most Tel Aviv fashion buyers got stuck with large stocks of orange items, as left-leaning Tel Aviv fashionistas refuse to buy anything in the hue.

According to police estimates, 10,000 demonstrators had arrived in Netivot by late afternoon. Settlers’ spokesmen put the number closer to 40,000. The rally came during a week that began with an escalation of mortar shelling by Palestinian Arabs into settlements and border towns from Gaza. Half a dozen Israelis were injured by mortar shells in nearby Shderot on Saturday. Several mortar shells were shot at Gush Katif settlements yesterday as Hamas and Islamic Jihad terrorists attempted to present the separation plan, scheduled to begin August 15, as a military loss for Israel.

Both sides in the Netivot demonstration said they want to avoid violence. The Southern District police commander, Uri Barlev, met several times with a leader for the settlers, Pinchas Wallerstein, in an attempt to coordinate movements by their followers. Despite isolated cases of violent skirmishes, most demonstrators avoided heated confrontations.

An unrelated arrest yesterday highlighted to many Israelis the potential for real violence by a small minority among the dedicated settlers opposing the evacuation of Jews from anywhere in the biblical land of Israel. A Jerusalem judge ordered two 20-year-old enlisted soldiers in the Israeli army, Meir Bartler and Haim Katz, to be held without bail after they were accused by police of planting a fake bomb in Jerusalem’s crowded central bus station to demonstrate their opposition to the government.

Most demonstrators yesterday, however, said they would defy police only by remaining in place patiently until the government changes its mind about the evacuation plan. Eli Cohen of Mevo Horon, a West Bank settlement, said that 300 of his neighbors drove here in 60 small cars to avoid being stopped, as many in buses were. Before leaving for Gaza, the settlers carefully prepared for a long stay, bringing along large supplies of food and water.

“We are not going to fight our brothers,” Mr. Cohen told the Sun. Two of his brothers-in-law, Mr. Cohen said, are policemen who he might meet across a barrier. But he could not swear that no violence would occur once the demonstrators entered Gaza, which, he said, was the main reason for coming here.

Whether to enter Gaza is not his decision to make, he said. “Our Rabbi, Jonah Dovrat, will tell us what to do,” Mr. Cohen said, hinting that the almighty and the rabbis overrule the government’s ideas of democracy, which were at the center of yesterday’s debate in Israel.