The crusades began in 1095 under Pope Urban II.

In the west, from the 11th century onward, older cathedral schools developed into universities (see University of Paris, University of Oxford, and University of Bologna.) Originally teaching only theology, these steadily added subjects including medicine, philosophy and law, becoming the direct ancestors of modern western institutions of learning.

Accompanying the rise of the "new towns" throughout Western Europe, mendicant orders were founded, bringing the consecrated religious life out of the monastery and into the new urban setting. The two principal mendicant movements were the Franciscans and the Dominicans founded by St. Francis and St. Dominic respectively. Both orders made significant contributions to the development of the great universities of Europe. Another new order were the Cistercians, whose large isolated monasteries spearheaded the settlement of former wilderness areas. In this period church building and ecclesiastical architecture reached new heights, culminating in the orders of Romanesque and Gothic architecture and the building of the great European cathedrals.

From 1095 under the pontificate of Urban II, the Crusades were launched. These were a series of military campaigns in the Holy Land and elsewhere, initiated in response to pleas from the Byzantine Emperor Alexios I for aid against Turkish expansion. The crusades ultimately failed to stifle Islamic aggression and even contributed to Christian enmity with the sacking and occupation of Constantinople during the Fourth Crusade.

Beginning around 1184, following the crusades brought about by the Cathar heresy, various institutions broadly referred to as the Inquisition, were established aimed at suppressing heresy and securing religious and doctrinal unity within Christianity through conversion, and prosecution, of alleged heretics.