They were intended to serve as a bulwark for the Roman settlements south of the Po, and to ward off from Italy the incursions of the migratory northern tribes and the aggressions of the predatory inhabitants of the Alps, who were wont to make regular razzias in these districts.

His army was soon ready to take the field, and his exchequer was filled by some razzias on a great scale; but the Carthaginian government showed itself far from desirous of despatching the declaration of war to Rome.

Abd-el-Kader then swept in a razzia to the south of Miliana, and soon appeared in full force in the Sahara as the bewildered French pursuers returned to their cantonments in despair of reaching him.