The years 1073–1198 witnessed the development of the papal legation as one of the most important instruments of papal government – the connecting link between the papal curia and the churches and secular rulers of western Christendom. This was an innovation of the reform papacy. The early medieval papacy had retained envoys (apocrisiarii) in Constantinople and subsequently at the Carolingian court to represent the interests of the Roman church. But the reform papacy began to use envoys on an unprecedented scale to implement its decrees and to promote its conception of the papal primacy throughout Christendom. This abrupt transformation of the Roman envoy into an instrument of reform occurred early in the career of Pope Gregory VII, who during the 1050s, as subdeacon (later archdeacon) Hildebrand, was one of the first to exercise the enhanced authority of a legate of the reform papacy. On his second legation in France (1056) he held a council in Chalon in which he deposed several bishops guilty of simony. His legatine duties also brought him to the German court and to Milan, soon to be the main focus of the curia's efforts to inculcate respect for the Roman primacy. The pattern of Hildebrand's early career – successful legations strengthening a cardinal's influence in the curia – was repeated in the careers of most of his successors.

Of the nineteen popes of the period 1073–1198, all except four had been active as legates.