Internationally, the order is governed by the Benedictine Confederation, a body, established in 1883 by Pope Leo XIII's Brief Summum semper, whose head is known as the Abbot Primate. Individuals whose communities are members of the order generally add the initials "OSB" after their names.
The monastery at Subiaco in Italy, established by Saint Benedict of Nursia c. 529, was the first of the dozen monasteries he founded. He later founded the Abbey of Monte Cassino. There is no evidence, however, that he intended to found an order and the Rule of Saint Benedict presupposes the autonomy of each community. When Monte Cassino was sacked by the Lombards about the year 580, the monks fled to Rome, and it seems probable that this constituted an important factor in the diffusion of a knowledge of Benedictine monasticism.
It was from the monastery of St. Andrew in Rome that Augustine, the prior, and his forty companions set forth in 595 on their mission for the evangelization of England. At various stopping places during the journey, the monks left behind them traditions concerning their rule and form of life, and probably also some copies of the Rule. Lérins Abbey, for instance, founded by Honoratus in 375, probably received its first knowledge of the Benedictine Rule from the visit of St. Augustine and his companions in 596.
Gregory of Tours says that at Ainay Abbey, in the sixth century, the monks "followed the rules of Basil, Cassian, Caesarius, and other fathers, taking and using whatever seemed proper to the conditions of time and place", and doubtless the same liberty was taken with the Benedictine Rule when it reached them. In Gaul and Switzerland, it supplemented the much stricter Irish or Celtic Rule introduced by Columbanus and others. In many monasteries it eventually entirely displaced the earlier codes.
By the ninth century, however, the Benedictine had become the standard form of monastic life throughout the whole of Western Europe, excepting Scotland, Wales, and Ireland, where the Celtic observance still prevailed for another century or two. Largely through the work of Benedict of Aniane, it became the rule of choice for monasteries throughout the Carolingian empire.