The papacy soon became essentially a feudal state, and the pope became a medieval (later Renaissance) prince engaged in many of the worldly activities that brought criticism on the church in later centuries. The fall of the Holy Land to the Turks in 1065 catapulted the papacy into the forefront of world politics, primarily because of the Crusades, most of which were judged to be military and economic disasters and many of which the popes directly caused or encouraged. During the 12th and 13th centuries, the bitter rivalries that rocked the secular and spiritual bastions of Europe took their toll on the stability of the Holy Roman Empire, which grew weaker as city-states buttressed by mercantile and trade-related prosperity grew stronger. In addition, France emerged as a strong nation in its own right during this period. Each investiture of a new bishop to any influential post became a cause for endless jockeying for power among many political and ecclesiastical factions.
These conflicts achieved their most visible impasse in 1303 with the full-fledged removal of the papacy from Rome to the French city of Avignon. For more than 70 years, until 1377, viciously competing popes (one in Rome, another under the protection of the French kings in Avignon) made simultaneous claims to the legacy of St. Peter, underscoring as never before the degree to which the church was both a victim and a victimizer of European politics.
The seat of the papacy was eventually returned to Rome, where a series of popes proved every bit as fascinating as the Roman emperors they replaced. The great families -- Barberini, Medici, Borgia -- enhanced their status and fortunes impressively whenever one of their sons was elected pope.
In the mid-14th century, the Black Death ravaged Europe, killing a third of Italy's population. Despite such setbacks, northern Italian city-states grew wealthy from Crusade booty, trade with one another and with the Middle East, and banking. These wealthy principalities and pseudorepublics ruled by the merchant elite flexed their muscles in the absence of a strong central authority.
