Furious protesters are denouncing Israeli security forces as "Nazis" - but this is not a scene from a pro-Palestinian rally on the streets of London or Paris. This clash is in the heart of Israel, in which hundreds of ultra-Orthodox men in white shirts, black fedoras and long black frock coats face off against the military police.

The flashpoint is a building in the city of Modi'in, midway between Jerusalem and Tel Aviv, where a young ultra-Orthodox Jewish (or Haredi) man lives. The police have come to arrest him after he failed to report for military service.

The clash in early October, seen by the BBC in a video, is one of many in recent months in which one of the deepest schisms in Israeli society has become ever more exposed.

This widening fault line is playing out against the backdrop of the wars Israel is currently fighting, including the unresolved conflict against Hamas in Gaza - as well as increasing violence by extremist settlers against Palestinians in the occupied West Bank.

Once a tiny minority, the ultra-Orthodox remain a group apart even as their numbers expand year by year. Currently, they are estimated to make up about 14% of the population, and the birth rate within the community remains far higher than among other Israelis. If their numbers continue to grow at a similar rate, they could make up one-third of the Jewish Israeli population by 2050.

As the ultra-Orthodox community becomes bigger, so has the debate around the expense of supporting them with stipends so they can devote themselves to full-time religious study. Subsidies to the group are estimated to cost the government 35bn shekels (£8.4bn) per year and, until recently, they were exempted from military service.

Now they're no longer an insignificant minority, they're facing pressure to engage more with wider Israeli society.

National security and the economy are two of the key issues this election. That means the division between the ultra-Orthodox and the majority of Israelis who believe they are not contributing their fair share to either is starker than ever.

With no outright majority likely for any current political alliance, and the future of Prime Minister Benjamin Netanyahu in doubt, the role of smaller parties - including Haredi parties - will once again be crucial in deciding who will govern Israel.

To have any chance of staying in power, Netanyahu needs to keep the ultra-Orthodox parties on side, however much pressure there is within Israel for their special status to be diminished.

From the ultra-Orthodox perspective, their social contract with the Israeli state is increasingly coming under pressure. Their all but exclusive focus on the study of Judaism's religious texts - such as the Torah, the Jewish Bible - means their education system is separate and many Haredim are not part of Israel's workforce.

For the ultra-Orthodox, the biggest issue of all is holding on to the exemption from serving in the IDF for students at traditional religious - or yeshiva - institutions. This dates back to the earliest days of the Israeli state when the Haredim were a miniscule community of survivors struggling to rebuild from the near extinction of the Holocaust.

But as Israel has become more embattled after the attacks of October 7, fighting wars on several fronts, their near complete absence from the country's conscription army has become more controversial.

Religious students and their rabbis believe that if young ultra-Orthodox men enter the military, they will be exposed to influences and behaviours that may decisively turn them away from their community. Beyond that, they believe that their staying true to the traditions of their community is vital for the very survival not only of Israel but the Jewish people.

When asked not long after October 7 why the ultra-Orthodox didn't contribute more to the military in such an emergency, one of the community's most senior leaders, Rabbi Dov Landau, said that not only should religious students not serve in the army, but they shouldn't even visit the wounded or attend the funerals of soldiers.

The rabbi said that in a time of such danger, only Torah students could protect Israel spiritually. "Salvation only comes through Torah learning, orderly Torah learning. And any neglect of or disruption to Torah learning, woe and alas for what will happen… The more Torah learners multiply, the more Torah learners increase their learning, the better. They protect us."

It would be a considerable understatement to say that this view is not shared by wider Israeli society. Polls have shown public support for conscripting the ultra-Orthodox surge throughout the war in Gaza. Many see it as a dereliction of responsibility by the Haredi community, made all the more galling by the fact that such a stance comes at the expense of taxpayers. The IDF has bemoaned a deficit in manpower, while many Israelis have had to serve hundreds of days in the past three years.

Dahlia Scheindlin is a leading political consultant and pollster in Israel. She says this issue is critical for Netanyahu and is key to understanding this moment in Israeli society against the backdrop of the war in Gaza, particularly among the political right. "Really the most burning, more immediate issue is the right-wing communities who are furious at the government for protecting the blanket exemption from the IDF at a time when, especially among the right, but really everybody in the Jewish community in Israel, is serving and many dying in these wars."

Two years ago, the Supreme Court ruled that the exemption for ultra-Orthodox men from serving in the military was effectively null and void. That could have meant that those dedicated to full-time religious study would now be drafted.

The reaction from the Haredi community was one of fury. Hundreds of thousands of Haredim held protests, blocking the main highways. And as with the incident in Modi'in, they tried to prevent the arrest of religious students for evading conscription. Protests have continued off and on, and densely-populated Haredi areas are often the backdrops for confrontation with the security forces. This is a row that is playing out in the election.

There are two parties that have traditionally represented the Haredi community. One is United Torah Judaism – or UTJ – and represents Ashkenazi Jews, or Jews of European origin. The other is Shas, which was formed later and represents the Sephardi and Mizrahi – Jews from North Africa and the Middle East. They share a core agenda, which puts religious study above all else, including any questions around relations with the Palestinians.

Both UTJ and Shas have been part of Netanyahu's coalition - and they used their political clout to find ways to try to block enforcement of the Supreme Court ruling. On several occasions, they threatened to pull out of the alliance and bring the government down. UTJ acted on this but continued to support the government from outside, while Shas remained within the coalition.

Centre-right politician Gadi Eisenkot, who's shaped up as Netanyahu's main rival in this month's election, does not support their stance. He has made clear his belief that the idea of the ultra-Orthodox constituting a separate state within Israel with its own rules has become increasingly toxic. "A country that sends its best sons and daughters to fight and sacrifice their lives cannot tolerate a reality in which a state within a state exists," he said.

All this has meant that the issue of conscription exemption for ultra-Orthodox men is the number one priority on the electoral agenda of both Shas and UTJ.

A recent remark by a UTJ parliamentary candidate, Eliakim Stark, has raised the temperature further. He compared the plight of ultra-Orthodox men evading the military draft to the persecution of Jews during the Holocaust. It triggered furious rebukes from opposition leaders from across the political spectrum.

Daniel Goldman, an activist who specialises in Haredi issues, says that the two main Haredi parties feel increasingly embattled and less open to compromise.

He says the ultra-Orthodox don't believe that the state really needs their boys to bolster numbers. "It's at least partly down to the fact that the Haredi parties see the state as wanting to take their boys out of the community and change them from ultra-Orthodox to either regular religious or secular, God forbid, as they perceive it," he says. "And so in that environment of tension, they've actually hardened their positions."

Yitzhak Goldknopf from the UTJ, a former minister, has gone so far as to issue an ultimatum: "The Haredim will not change their way of life because there is an army and a war... If there is no choice and they must leave the country, they will leave." But this is having a clear impact on the electoral fortunes of the Netanyahu coalition - of which Shas in particular has long been a key part. Without them, Netanyahu's alliance would fall short of the more than 60 seats needed for a majority in the Knesset.

Dahlia Scheindlin, the Israeli pollster, says that the refusal to give up the draft exemption by Shas and UTJ is damaging Netanyahu's coalition. "It is one of the main reasons why the coalition is unable to win back the kind of support that they had in 2022 when they won 64 seats," she says. "They're currently polling at about 50 to 52 seats." All Netanyahu's challengers advocate for ending the ultra-Orthodox exemption and cutting funds to institutions or individuals who refuse the draft. On the left, Yair Golan has called for an immediate mobilisation of those who are eligible.

So, despite statements from Shas and UTJ that they would switch allegiance from Netanyahu if he were to dilute his support, there seems for now nowhere else for them to go.

Anshel Pfeffer has been a leading commentator on the Israeli political scene for years - now mainly as the Economist's correspondent in Israel. He says Netanyahu's position looks shaky. "There are two things that are bringing together the current opposition bloc," he says. "One is obviously they want to replace Netanyahu and the other is they are capitalising on this really hostile environment nowadays towards the ultra-Orthodox, mainly over the issue of the draft to the army.

"Netanyahu has been willing for many years, to basically give the ultra-Orthodox whatever they want. They're not going to get that from the opposition." Into this arena of resentment and intransigence, a new Haredi party has emerged this year, presenting itself as a break with the traditional mindset of Shas and UTJ.

Essentially, the Haredi Public Party is offering a compromise in which the ultra-Orthodox would contribute more to Israel as a whole while maintaining the core of their identity. For the first time in the ultra-Orthodox community, it is also fielding two female candidates. One of them, Ziva Ginz, explained to the BBC her party's position on the military draft. Key to it is men serving being allowed to remain culturally Haredi. "Anyone whose life is genuinely devoted to full-time Torah study should be able to continue learning. Everyone who isn't sitting and studying for a full day should serve alongside the rest of Israeli youth, in frameworks where a young man can enter as a Haredi and finish as a Haredi," she says.

But it may be too soon for such efforts at compromise to make an impact this election.

Anshel Pfeffer says that it's difficult to sway the base vote in the ultra-Orthodox community, where most still essentially follow what their rabbi says they should do.

"And once people are voting for other parties, they won't necessarily do so for another Haredi party," Pfeffer explains. "That's why we're seeing people like [far-right leader and National Security Minister Itamar] Ben-Gvir making inroads in the Haredi community, because he's the only non-Haredi party leader who actually talks to young Haredi. Basically, every other party in Israel doesn't even try." This is reflected in the polls, which show his Jewish Power party is making gains.

If Ben Gvir's actions are increasingly seen as tainting Israel's international image with his support for policies such as annexing the occupied West Bank, his hard-right message is attracting a bigger core of support within the country. His ultra-nationalist ethos is not one that traditionally overlaps with policies of the Haredi parties, but they share a position on the right of Israeli politics.

So for some ultra-Orthodox voters looking for a new political home, Ben Gvir represents the nearest alternative. His self-portrayal as a strong man unafraid to take an extreme position against those he perceives as Israel's enemies in the face of international condemnation may attract some already leaning to the far right in the Haredi community.

No alliance appears close to achieving a majority, however, so there is bound to be a lot of horse trading to secure a workable coalition after the vote.

Netanyahu will naturally apply his exceptional political skills to trying to find one way or another to stay in power.

As ever, that leaves the smaller parties with the ability to play the role of kingmaker. That's a role that the ultra-Orthodox parties have been known for in the past. But this time they may not be the decisive factor.

"The truth is, any small party can become a kingmaker," Dahlia Scheindlin says. "I don't think it would take too much to lure the Haredi parties away from Netanyahu... The thing is, though, I don't think the opposition parties will want to lure them in unless they have some promise that they're really prepared to make serious concessions on the draft. The opposition parties are absolutely staking their platforms and their promise to the voters on that issue." This time, rather than being the kingmakers, it may turn out that the ultra-Orthodox parties help bring down the king. Lead image: AFP via Getty