JERUSALEM — On one level, the questions shaking the Israeli political system this week are pragmatic: how many ultra-Orthodox men and Arab citizens should be drafted into the military or national service, over how many years and how should those who resist be penalized?


But the debate over these details masks a more fundamental and fractious one about evolving identity in this still-young state, where a “people’s army” has long been a defining principle, and about the growing cleavage among its tribes.


That is what has brought Prime Minister Benjamin Netanyahu’s broad unity coalition to the brink of collapse in recent days, with an Aug. 1 deadline looming to replace a law providing draft exemptions to thousands of men studying in yeshivas that the Supreme Court deemed illegal in February.


The leader of a committee that Mr. Netanyahu appointed — and this week disbanded — to prepare a replacement law released a 100-page report on Wednesday that called for 80 percent of the ultra-Orthodox to serve in the military by 2016, and for fines of about $25,000 for those who do not.


Shaul Mofaz, the Kadima Party leader whose surprise alliance with Mr. Netanyahu two months ago created an unheard-of 94-seat majority in the 120-member Parliament, said Wednesday that he would quit the coalition within days if the committee’s work did not form the basis of the new law. But religious and right-wing factions have also vowed to bolt the coalition if personal sanctions are included or Arabs are not drafted as well.


“It’s a possibility of civil war between sectors,” said Yedidia Stern, who runs a program on religion and state at the Israel Democracy Institute, and served on the committee charged with rewriting the draft law.


“What’s at stake is two cultures, two civilizations,” Professor Stern added, referring to the ultra-Orthodox, known as Haredim, and other Jews here. “These two civilizations used to live in some kind of peace because each one thought that the other is going to disappear eventually. Nowadays I think everybody realizes that the two camps are here to stay, and we have to decide what will be the identity in the public sphere.”


At issue is not so much the pragmatic needs of the military, where integrating large numbers of Haredim promises to be more hassle than help, but a growing resentment over who serves the state and who reaps its rewards. Last year, about 17 percent of 18-year-old Haredim joined the Army, compared with about 75 percent of other Jewish men; an additional 14 percent of Haredim and 8 percent of Arab citizens signed up for civilian service. Over all, just over half of Israelis now do military duty, a far cry from the generally accepted notion that there is a universal draft.


Because the military is the critical gateway to employment here, there are deep economic implications as well: some 56 percent of Haredim live in poverty, and the average annual income in their community is about half that of the national norm, with many of their large families relying on welfare, housing grants and subsidies for yeshiva study.


If demographics are destiny, it makes sense that this long-simmering tension is reaching a rolling boil. While Haredim account for less than 10 percent of Israel’s seven million citizens, and Arabs 20 percent, their high birthrates mean that about 46 percent of today’s kindergartners come from the two groups, growth that is “challenging the basic formula” of Israeli society, according to Aluf Benn, editor of the left-leaning newspaper Haaretz.


“These groups don’t want a larger slice of the pie, they want a different recipe,” Mr. Benn said in an interview. “If Israel defines itself as a Jewish democratic state, the Arabs would do away with the Jewish part, and the ultra-Orthodox at least in their dream would get rid of the democracy. They respect the authority of the rabbis.”


Einat Wilf, one of five lawmakers who served on the committee, said that the solution was not a universal draft, but an acceptance that “the people’s army” is a fiction — and a reworking of benefits accordingly.