Ultra-Orthodox Jews - known in Hebrew as "Haredim," or "those who tremble" before God - have a birthrate far higher than that of other Israeli Jews, with 10 children in a single family not uncommon. They seem poised to become far more numerous and influential.
Relations between Haredim and other Israelis have never been smooth. Critics have long complained that they shun work in large numbers in favor of religious study, rejecting mainstream Israel even as they rely on that mainstream for financial support.
But increasingly, even some Haredim share a sense that things cannot continue as they are.
"The Haredim have set up a state within a state and have a long conflict with the state of Israel, which is now on the eve of an explosion," said Kobi Arieli, a popular radio host and author from the liberal edge of the Haredi community. "There is no chance that this situation will continue."
Many community leaders chafe at change, and are especially sensitive to secular concerns about their growing population.
"What does society want us to do, kill ourselves? Our community is a fact and everybody needs to understand that we exist and are not going anywhere," said Rabbi Shmuel Pappenheim, a spokesman for the Eida Haredit, an umbrella group of ultra-Orthodox factions. "This community will continue to thrive and nobody can change it."
Part of the issue is the community's poverty: About half of ultra-Orthodox adults do not work, and many men are full-time Torah students with government stipends that anger the secular majority but are nonetheless quite meager. Of the estimated 700,000 Haredim in Israel - around 9 percent of the population - just under 60 percent live below the poverty line.
If Haredim don't begin working in larger numbers, the financial daily The Marker posited this week, "this threatens Israel's future."
Perhaps the most corrosive issue is the military draft. Israel's early leaders agreed to support seminaries and issued several hundred draft exemptions, but over the decades, as the number of ultra-Orthodox Jews ballooned, so did the number of full-time students with exemptions. Today there are around 50,000. The law that exempts them requires them not to work, lest they lose their exemptions. The arrangement that has resulted is unique to Israel; abroad, ultra-Orthodox Jews work and their communities support themselves.
Last week, in unusually strong language, Israel's military chief, Lt. Gen. Gabi Ashkenazi, criticized Israelis who do not serve in the army, including the masses of young Haredi men. Those who do not serve should be "ashamed," Ashkenazi said.
That feeling is widely shared, and pressure is growing to find ways to draft Haredi youth. But the community's strong political parties have foiled attempts to reduce the draft exemptions, cut funding, or force ultra-Orthodox schools to teach basic subjects like English, math and science.
Socially and politically conservative, the ultra-Orthodox parties prefer to align with rightist coalitions that have pursued more hardline policies. Although they have supported left-leaning governments as well - generally when these had majorities without them anyway - Prime Minister Benjamin Netanyahu has described them as his natural allies.
The Haredi lifestyle is inspired by the Jewish world of eastern Europe that was destroyed in the Holocaust. Comprising a mosaic of sects and factions of varying shades and beliefs, they share a tendency to reject a secular society they see as morally corrupt and to sanctify religious study, modesty and charity.
In Israel's early days, the precursors of today's Haredim rejected Zionism and pioneered what they called the "learning society," which meant that all young men - and not just a small intellectual elite, as had been the case in Europe - were to devote themselves to religious study instead of work. This was meant to restore the world of Torah scholarship that had been destroyed by Nazi Germany. Over the years, many Jews who emigrated to Israel from the Arab world also have joined this camp.
They mostly live in separate neighborhoods and study in separate schools, with little interaction with a majority that has largely come to view them as a burden.
The interactions that do exist are charged, with secular Israelis often resenting what they see as attempts to impose Haredi religious mores on others. This month, for example, saw tiffs over gender segregation on some bus lines in Haredi neighborhoods, and over similar segregation at a concert in a secular area to be attended by Haredim.
Because it is difficult to precisely define who is Haredi and who is not, exact figures on the community's population and birthrates are difficult to come by. A November 2010 report by two demographers at Haifa University, Arnon Soffer and Evgenia Bystrov, estimated that 30 percent of the Jewish newborns are now Haredi. Government statistics predict that by 2025 the Haredim will have jumped from 9 percent of the population to 15 percent.
"We are not yet seeing the full strength of the process of ultra-Orthodox growth," the demographers wrote - this "will be felt when the young generation reaches the age of military service and work." The demographers warned that the economy would not be able to support a bigger Haredi population.
Alongside those concerns is a nascent feeling that change is slowly coming.
Ultra-Orthodox society is not monolithic or static and there are signs of movement, said Sergio DellaPergola, a demographer at Hebrew University in Jerusalem.
The number of ultra-Orthodox men serving in the army or performing national service has quietly inched upward from almost none a decade ago to several thousand today, and the government voted this week to encourage more to join. The army has formed special programs tailored to ultra-Orthodox needs, where men can serve in male-only environments and eat food meeting the strictest standards of Jewish dietary law.
Over the same period, the number of Haredim in professional training programs has risen from several hundred to 6,500, The Marker reported. The number of Haredi men with jobs has risen 8 percent in eight years.
This foreshadows greater changes, said Arieli, the Haredi author. Many young Haredim, he said, are simply unwilling to live in isolation and poverty.
"It will happen slowly," he said. "From year to year more and more Haredi youth will join the army and go to work. This is what is already happening, and it will change everything."