The four monasteries claimed immunity from secular control, but the counts of Flanders engineered their own appointment as lay abbots, acquired this control for themselves, and thereby consolidated their own position of power within the county.
The territories of the early Flemish counts were referred to collectively as "Flanders" in contemporary documentation only from the early 1000s.
Count Baudouin II expanded his territory into Courtrai, seized control of the counties of Boulogne and Ternois, and acquired the lay abbacy of St Bertin.
Further territorial expansion was undertaken by Arnoul I Count of Flanders, who also seized the abbacy of St Vaast.
Whatever the precise process by which the march of Flanders evolved, by the late 11th century the counts of Flanders were firmly established in that territory and therefore owed allegiance to the French king for the western part of their county and to the German emperor for the eastern part.The possible ancestry of Baudouin I Count of Flanders is set out in Chapter 1. None of the individuals named is referred to in surviving contemporary primary sources, although it is impossible to assess whether the later sources were based on earlier documentation which has since disappeared.Information relating to these individuals is incomplete and, in part, contradictory.These abbacies of St Bertin (near St Omer), St Vaast (in Arras), and St Peter and St Bavo in Gent were founded during the period of gradual christianisation of Flanders and evolved into powerful local communities with extensive landholdings.This process of evolution was presumably facilitated by their relative remoteness from the headquarters of the French archbishopric of Reims, whose ecclesiastical jurisdiction including the county of Flanders.