population. From the 6th century on, the no-mans-land farther north was filled by Franks from the Rhinelands and other Germanic groups from the Netherlands and Germany.

The first wave of immigration in the present day Flemish territory was accompanied by limited Christianisation. In the wake of the immigrants, missionaries tried to convert the heathen population, but had little success. The bishoprics were reinstated, usually with the same natural borders of the Late-Roman era; the Silva Carbonaria