These physical conditions must have favoured the guerrilla warfare waged for four years by the various Celtic tribes against the Roman invader, and it is no doubt partly to them that the old "Belgæ" owed their reputation of courage and fortitude. These tribes, occupying the Scheldt and Meuse valleys, formed the rearguard of the Celtic wave of invasion which, coming from the East, had spread across Western Europe. At the time of the Roman conquest they were already closely pressed by a vanguard of Germanic tribes which had settled in Zeeland and on the left bank of the Rhine, so that even at this early stage of Belgium's history we find the dualistic character of Belgian civilization marked in the division of the country into two Roman provinces, "Belgica Secunda," in the west, and "Germania Inferior," in the east.
ROMAN INFLUENCES
The immediate effect of the Roman conquest, which was far more rapid than in Britain, was to stop for a time the influx of German tribes by the establishment of a solid barrier along the Rhine. The colonists of German origin were soon absorbed by the old inhabitants of the country, and were subjected with them to the powerful influence of Roman culture. Celts and Germans alike became Belgo-Romans, and adopted the trade and the institutions of their conquerors.
As far as we can make out from the scanty documents at our disposal, Roman civilization moved along the Rhine towards Cologne, whence a great Roman highway was built towards the West, crossing the Meuse at Maestricht and, following the edge of the Coal Wood, through Tongres and Cambrai to Boulogne. This road, known through the early Middle Ages as the "Road of Brunehaut," was for a long time the main way running from east to west in a country where all the important streams, such as the Meuse, the Scheldt and their tributaries, ran from south to north. The extent of Roman influence may be gauged by the position which the various parts of the country occupied towards this highway. Tongres and Tournai still possess Roman remains. The foundations of Roman villas are found in the provinces of Namur, Hainault and Artois, while all traces of Roman occupation have disappeared from Flanders. The sandy and marshy nature of the soil in Northern Belgium may to a certain extent account for this fact, and we know that, in some instances, the stones provided by old Roman structures were used, in the Middle Ages, for the construction of new buildings. But it can nevertheless be assumed that, generally speaking, communications remained the principal factor of Roman civilization in these far-away marches of the Empire, and that Roman influence, so strongly felt on the Rhine and along the Meuse, became gradually less important as the distance increased. The country was almost exclusively agricultural, but it is interesting to note, in view of later developments, that, even at this remote period, the Menapii, who dwelt in Flanders, had acquired a reputation for cattle breeding and manufactured woollen mantles which, under the name of "birri," were exported beyond the Alps.
Though strongly influenced by Rome in their trade and methods of agriculture, the Belgo-Romans had retained their language and religion. Romanization, in the full meaning of the word, only began during the last years of the third century, under the influence of Christianity. During the third century, the bishopric of Trèves included the whole of "Germania Inferior." A special bishopric was established subsequently at Cologne, and, about the middle of the fourth century, at Tongres. Others appeared later at Tournai, Arras and Cambrai. This gradual spread of Christianity, which moved along the same roads as Roman civilization, from Cologne towards the West, only reached Flanders half a century later.
The Christianization of the country must have been far from complete when the incursions of the Germanic tribes, greatly encouraged by the gradual decline of the Roman Empire, brought a sudden and dramatic change in the life and development of the two Roman provinces.
THE FRANKS
During the third and fourth centuries, the pressure of the Germanic tribes, which had been considerably delayed by the Roman conquest, reasserted itself. The Rhine frontier was subjected to repeated assaults, which the depleted legions were no longer in a position to repulse effectively. The Franks attacked from the east and the north through Zeeland, while part of the Saxons who attacked Britain raided at the same time the Belgian coast. In spite of the military successes of the Emperors Constantine and Julian, the situation became so threatening that a second line of defences was fortified on the Meuse and along the great Roman highroad running from Tongres to Tournai. In 358, Julian authorized the Franks to settle in the sandy moors east of the Scheldt (Toxandria), and when, at the beginning of the fifth century, Stilicon recalled the legions in order to defend Italy against the Goths, the German tribes, finding themselves unopposed, invaded the country of the Scheldt and the Lys, reducing into serfdom the old inhabitants who had escaped massacre. The Rhine ceased henceforth to be the Empire's frontier. The latter ran now along the great highway from Tongres to Arras. Before their second line of defences the Romans, under Ætius, put up a last fight, but they were defeated by the Frankish king Clodion, who extended his kingdom along the coast as far as the Somme and established himself at Tournai (431), where his grave was discovered twelve centuries later.
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