ON THE FACE OF IT, medieval crusading appears to have little to do with the creation of modern secular Europe. The crusades were a form of Christian holy war characterized by demonizing rhetoric, spiritual enthusiasm, religious ceremonies, ecclesiastical institutions, political objectives, social climbing and status-seeking. They speak of a society at once intensely local--region, city, lordship--yet ideologically wedded to universals: church, faith, empire, papacy. Yet from the growth of the idea of a nation specially favoured by God--familiar even today as in 'One Nation Under God'--to techniques of mobilizing political consent and fiscal exploitation, crusading fed into the establishment of states in which public religion became the servant, not the arbiter, of the civil community. The first western European income tax was probably the levy authorized by Henry II of England in 1166--imposed for crusading purposes. Some of the earliest national extraordinary lay or clerical taxes in medieval France or Germany were levied in the twelfth century for the Second and Third Crusades. After the church developed regular taxation of ecclesiastical property for the crusades in the thirteenth century, secular rulers attempted--successfully in most cases--to annexe this power to themselves. The need of the authorities to persuade and the expedients of bottom-up organization held together most large-scale eastern crusades as much as the ties of lordship, cash or coercion; and behind the religious propaganda and glamour, crusading helped stimulate the political engagement of a wide civil society, characterized by discussion and debate. By the later Middle Ages, lay powers felt the need to control such diversity, a process that contributed directly to the consolidation of nation-states. All this may sound a far cry from the efforts of the 'armies of God' to win terrestrial space to match the limitless sovereignty of their Maker.
Crusading developed from a military expedition of western European arms-bearers summoned by Pope Urban II in 1095 as a war of liberation to free the eastern Church in the Holy Land and restore to Christendom the Holy City of Jerusalem. This liberation operated on two levels; temporal, in expelling the Muslim rulers of Syria and Palestine; and spiritual, in the pope's offer of full remission of the penalties of confessed sin to those who, with selfless intent, undertook this campaign. In recognition of their commitment and adoption of a privileged religious obligation, participants received a cross--usually of cloth--to sew onto their garments. They become crucesignati, people (not all of them were men) signed with the cross, crusaders.
Such a war was not simply just--fought for religious reasons, a good cause or to regain lost lands--but holy, a religious duty demanded by God, Deus vult. Even the plunder, fighting and killing were part of a transcendent, penitential act. Christian holy war, to modern observers a conceptual oxymoron, boasted a long pedigree. Its intellectual roots lay in the militancy of the Old Testament, lent academic support by Roman doctrines of legitimate public war reordered to suit the Christian empire in the fourth and filth centuries. Practical antecedents came in the wars of the Christian rulers of early medieval Europe against Arabs, Magyars, Scandinavians and Slavs. To this tradition of acceptable warfare against infidels was added ecclesiastically-sanctioned violence against Christians who infringed church property rights or opposed the papal temporal, as well as spiritual, authority over Christendom.
Urban II's penitential war became an established weapon in the Church's armoury. Over the next two centuries, crusading objectives extended from the Holy Land to the protection and expansion of the secular boundaries of Christendom, in Iberia and the Baltic, the political interests of the papacy and its political allies, and the integrity of Christianity itself against internal dissidents and heretics. …