The Haredi world contains two currents that spent the eighteenth century in bitter conflict with each other and now stand together against modernity. The history explains a good deal about the internal texture.
Hasidism began in the Ukrainian and Polish borderlands around Israel ben Eliezer, called the Baal Shem Tov, who died in 1760. It was a popular revival, drawing on Kabbalah and offering ordinary Jews without Talmudic learning a way to serve God through joy, fervour, song and attachment in prayer, and it gathered around a charismatic tzaddik or rebbe, a righteous man whose blessing, table and person mediated the divine to his followers. The court, the dynasty and the hereditary succession all follow from that.
The Mitnagdim, the opponents, formed around the Vilna Gaon, who issued bans of excommunication against the Hasidim in 1772 and after. Their objections were serious: that a movement organised around a man was idolatrous in tendency, that it disparaged Talmudic learning, and that its ecstatic practice was undisciplined. Their answer was the modern yeshiva, Volozhin, founded in 1803, and its descendants, built on rigorous, full-time, lifelong Talmud study as the highest form of service.
The two settled into coexistence during the nineteenth century, when both concluded that the real threat was the Haskalah, the Jewish Enlightenment, and the secularisation that followed it. The word Haredi, from a biblical phrase meaning those who tremble at God's word, now covers both, and the Yiddish-speaking world it describes was substantially destroyed in the Holocaust and rebuilt from remnants in Israel, New York, London and Antwerp with striking speed.