Linked by a thread that unravelled

Lionel Kochan is one of Britain's neglected academic treasures.

He has written on subjects as varied as the Russian Revolution and the Nazi persecution of the Jews, and he is as much at home with rabbinic texts as with the diplomatic records of the Habsburg Empire. His erudition and linguistic range is staggering. Now he has poured decades of accumulated knowledge into this, his magnum opus. Although it can be hard going, with densely written paragraphs spreading over more than a page, to the patient reader he offers a cornucopia of material articulated around a tightly worked argument about the modernisation of Jewish society.

This subject has preoccupied the greatest Jewish historians. To Heinrich Graetz, the Jewish Middle Ages ended with the infusion of Enlightenment thought into Jewish life via the philosopher Moses Mendelssohn. Simon Dubnow saw the French Revolution as the hinge on which Jewish modernity turned. It provided the conditions under which Jews could acquire citizenship, transforming them into political actors, first as members of the nations into which they integrated and, later, in the service of their own people. Salo Baron attributed the transformation to the dual forces of centralisation and capitalism eroding the traditional Jewish community. The Zionist historians of the "Jerusalem School" identified modernity with the dawning of national consciousness.

In this great historiographical tradition, Kochan stands closer to Dubnow and Baron than to Graetz or the Jerusalem School. In a sense, he writes political history; but his subject is a polity grounded in faith.

At the start of the period every Jew lived in a kehillah , an autonomous community. The story of the kehillah provides the thread that unites the Jewish experience despite the Jews' dispersion across the continent. The kehillah supplied a place of worship and burial, functionaries to circumcise male children and provide food prepared according to Jewish law, schools, and welfare for the old or indigent. Most crucially, it enabled the Jews to live according to Jewish law, by the rhythm of Jewish time, under the tutelage of their rabbis. The kehillah also raised taxes from the Jewish community, both to fund its internal services and to pay off the gentile authorities, who charged Jews a high price to live and trade in peace. These diverse functions created endless tension. Who was to rule the kehillah : the rabbis or the rich? The answer tended in one direction only, and Kochan demonstrates that the changing environment in early modern Europe inexorably benefited the Jewish secular elite.

The Thirty Years' War damaged many Jewish communities but strengthened others and even offered opportunities for Jews to resettle areas from which they had been expelled. Rulers who were desperate to generate revenue offered charters to lure Jews. These regulatory regimes came at a price, but they allowed precarious bridgeheads to form. Attacks on these fledgling communities by resentful merchants, counter-reformation clerics or Jew haters such as Empress Marie Theresa strengthened the mercantile class, which alone could mobilise the financial muscle and connections to resist. Ironically, tolerance was equally threatening to rabbinical leadership. Easy-going and utilitarian port cities such as Livorno, Venice, Hamburg, Amsterdam and London witnessed the emergence of a new Jewish type: the cosmopolitan, sceptical ex-Christian. Like the court Jews of Vienna and Berlin, they aped gentile manners and bullied the rabbis they hired. In an early lament on assimilation and secularisation, Rabbi Hart Lyons moaned: "In London, I had money but no Jews. In Mannheim, Jews but no money. In Berlin, no money and no Jews."

The growth and impoverishment of the Jewish population, hemmed in by restrictive laws governing residence rights and occupational opportunities, added to the tension straining the kehillah . To Kochan, the Mendelssohnian revolution in Judaism was an almost incidental rearguard action. Ultimately, the Jews were the objects of state policy. The kehillah succumbed to policies of forced integration, such as those imposed by Joseph II in the Habsburg Empire, or the conditions for civic equality demanded by the French revolutionaries. Its demise deprived Jews of the space that allowed them to preserve their faith-based identity, exposing them to the chill winds of both assimilation and anti-Semitism.

Kochan analyses Jewish society with pitiless clarity, although there is a hint of nostalgia for the era when learning conferred prestige and the right of leadership. But he has little time for the idealistic historiography that once dominated the field. While soaked in an appreciation of Jewish tradition, he has given us an unapologetically modern history of the Jews.

David Cesarani is research professor in history, Royal Holloway, University of London.