In the High Middle Ages, monarchs across Europe embarked on a program of political centralization, concentrating power in their own hands while expanding the reach and effectiveness of royal administrative and legal institutions. This process did not move forward in the same way in every kingdom, however, and it was not universally successful. In France and England, a series of reforming monarchs laid the foundation for further centralization, even as local elites developed institutions designed to ensure their continued participation in royal decision-making. In contrast, Otto I’s efforts in Germany were ultimately undone by the fallout from the long struggle with the papacy for control of northern Italy. At the same time that European monarchs sought greater control over their kingdoms, reform-minded leaders of the Roman Catholic Church sought greater control over church officials. The tensions created by these mutually exclusive objectives exploded in the eleventh-century controversy over lay investiture — the appointment of church officials by secular rulers. Church and state were not always at war, however, and often found ways to work together to the benefit of both. When, in 1095, Pope Urban II called on Europe’s secular leaders to join in him in a crusade to reclaim the Holy Lands, they responded enthusiastically, sensing that their association with a holy cause could only serve to increase the scope and legitimacy of their power. ■