BROOKLYN — The Barclays Center was filled with men wearing black and white Sunday, but it wasn’t the Brooklyn Nets battling an NBA foe. It was nearly 20,000 men from the Satmar Hasidic community protesting the Israeli army’s efforts to draft young ultra-Orthodox Jewish men.

The event, dubbed “Kinus Harevavot,” or “Gathering of Thousands,” was organized by the Williamsburg, Brooklyn-based Satmar organization Central Rabbinical Congress of the U.S.A. and Canada. It brought in school busloads of Hasidim from upstate Monsey, New York, and Lakewood, New Jersey.

The men — and it was only men and boys — filled the arena to capacity, listening to a long string of speeches in Yiddish from a dais positioned under a temporarily raised basketball net.

Among the speakers was the leader of the Williamsburg sect of the Satmar community, Rabbi Zalman Teitelbaum. After his father’s death, his brother Aaron Teitelbaum split off and now leads a Satmar community in upstate New York. The Aroynem, as the latter’s followers are known, boycotted the event.

The rally aimed to show the Israeli government that the anti-Zionist community in the United States supports its religious kinsmen in the Holy Land who resist serving in the Israel Defense Forces, said Rabbi David Niederman, who runs the Central Rabbinical Congress.

“We feel very strongly that there should not be and could not be a State of Israel before the Messiah comes,” he said. “We are forbidden to be part of the army.”

Niederman accused the Israeli authorities of manipulating unsuspecting Haredi, or ultra-Orthodox, youths into enlisting, and throwing them in jail at the first opportunity.

Open gallery view Rabbi David Niederman showing photos of what the organizers of an anti-IDF Satmar rally call Israeli police brutality against the Haredim, Brooklyn, June 11, 2017. Credit: Debra Nussbaum Cohen

“They are using every trick in the book to entice,” he said. “They are spending hundreds and thousands of shekalim to have people go in who are religious, on payroll, to promise the world for those who are going to enlist. Promising jobs and so on.”

As he told Haaretz, “We are here to tell our brethren ‘we are behind you and we will do whatever is in our power, and we have a major power.’”

The event was also meant to protest what Niederman called the Israeli authorities’ “brutality” against anti-Zionist Haredim. He leafed through a stack of enormous enlargements of photos showing men and boys being ill-treated. Holding up one of a young boy with long side curls being held in a headlock by a smiling policeman, he said mournfully, “Look. Look at this. We are dealing with persecution of religious Jews by Jews.”

Satmar organizers selected a name for their effort to evoke the Israelites’ enslavement under Pharaoh, calling their campaign “Let Our People Go.” They published a video of police beating Israeli Haredim, with dramatic sound effects underscoring their point.

In recent years, the issue of Haredim and the IDF has been fought in both the Knesset and the streets of Mea She’arim, an ultra-Orthodox neighborhood in central Jerusalem. Angry mobs of Haredim attack anyone — including fellow Haredim — they find in a soldier’s uniform.

Earlier this month police entered Mea She’arim to try to arrest people who harass Israeli soldiers. But their effort on a Friday, which employed detectives dressed like Haredi soldiers, backfired and only proved the event organizers’ point, Niederman said.

Also at issue is that voluntary enlistment has proved more popular among Haredi young men than their community leaders might like.

Open gallery view At anti-IDF Satmar rally at the Barclays Center, Brooklyn, June 11, 2017. Credit: Debra Nussbaum Cohen

People “understand that you don’t go out as you came in” after serving, Niederman said. The Israeli government “wants the Haredi community to become less Haredi, to assimilate. It’s very clear that is the motivation,” he said. “It’s forced assimilation.”

The Satmar community is worried about the “preservation of culture, preservation of a way of life,” said Shraga Feigenbaum, a public relations coordinator for the event. “The question is: Is the need for more soldiers enough that they can justify drafting the ultra-Orthodox, considering that the emphasis in the IDF today is on a smaller, leaner, more technologically savvy army?”

Niederman said rally organizers hoped to influence American lawmakers who give Israel billions of dollars in defense aid. If the U.S. and Israeli governments don’t pay heed, the Satmar community will take additional steps, he said, though he declined to give specifics. “We don’t want to go there yet,” he said. “I hope we never have to go there.”

Niederman also demurred when asked how much it cost to rent the Barclays Center for the rally and who provided the funding. No matter what it cost, “it is cheaper than losing one Jew,” he said.

Participants came by school bus from Monsey and by subway from Borough Park, Brooklyn. A delegation of rabbis flew in from the U.K. and Central America, organizers said.

But many of those from relatively near Kiryas Joel, New York, boycotted the rally, calling its participants sikriki after the Israeli Haredi extremists responsible for violence against those they deem Zionist.

While the scene inside was orderly, traffic outside was as chaotic as when Justin Bieber gyrated in the front window of his tour bus after a Barclays performance.

Never a community known for understatement, the Satmars closed their rally with a cantor reciting Psalms, his voice rising and falling as he pleaded with God to forgive their collective sins and save them. While a roaring crowd often shakes the arena after a Nets slam dunk, the sound of nearly 20,000 men responding as one to their prayer leader was another kind of roar altogether.