preside over church councils and make the pope’s influence felt outside Italy,
especially in France and Germany. To the papal curia Leo brought the most zealous
church reformers of his day: Peter Damian, Hildebrand of Soana (later Pope Gregory
VII), and Humbert of Silva Candida. They put new stress on the passage in
Matthew’s gospel (Matt. 16:19) in which Christ tells Peter that he is the “rock” of the
church, with the keys to heaven and the power to bind (impose penance) and loose
(absolve from sins). As the successor to the special privileges of Saint Peter, the
Roman church, headed by the pope, was “head and mother of all churches.” What
historians call the doctrine of “papal supremacy” was thus announced.
Its impact was soon felt at Byzantium. On a mission at Constantinople in 1054 to
forge an alliance with the emperor against the Normans and, at the same time, to
“remind” the patriarch of his place in the church hierarchy, Humbert ended by
excommunicating the patriarch and his followers. In retaliation, the patriarch
excommunicated Humbert and his fellow legates. Clashes between the Roman and
Byzantine churches had occurred before and had been patched up, but this one,
though not recognized as such at the time, marked a permanent schism. After 1054,
the Roman Catholic and Greek Orthodox churches largely went their separate ways.
More generally, the papacy began to wield new forms of power. It waged
unsuccessful war against the Normans in southern Italy and then made the best of the
situation by granting them parts of the region—and Sicily as well—as a fief, turning
former enemies into vassals. It supported the Christian push into the taifas of al-
Andalus, transforming the “reconquista”—the conquest of Islamic Spain—into a holy
war: Pope Alexander II (1061–1073) forgave the sins of the Christians on their way
to the battle of Barbastro.
THE INVESTITURE CONFLICT AND ITS EFFECTS
The papal reform movement is associated particularly with Pope Gregory VII (1073–
1085), hence the term “Gregorian reform.” A passionate advocate of papal primacy
(the theory that the pope is the head of the church), Gregory was not afraid to clash
directly with the king of Germany, Henry IV (r.1056–1106), over church leadership.
In Gregory’s view—an astonishing one at the time, given the religious and spiritual
roles associated with rulers—kings and emperors were simple laymen who had no
right to meddle in church affairs. Henry, on the other hand, brought up in the
traditions of his father, Henry III, considered it part of his duty to appoint bishops
and even popes to ensure the well-being of church and empire together.
