Why were the germanic tribes able to crumble the mighty roman empire?

Answer 1

The Germanic tribes invaded the western part of the Roman Empire and caused it to fall. The eastern part of the Roman Empire was not affected by these invasions and continued to exist for another 1,000 years.

The Germanic invasions were part of Migration Period. In this period many peoples north and east of the Roman Empire were migrating. Several Germanic peoples migrated from northern Europe to central Europe. There were also migrations by the Scythians (Iranian-speaking peoples) and the Huns from Asia into eastern Europe. This created a squeeze in central Europe and some Germanic peoples from that area (the Vandals, Sueves, Alans and Burgundians) migrated into Gaul and then also into Spain, and northwest Africa. These invasions were more than military actions. They were migrations which often involved the movement 100-150,000 people for each of these peoples. Moreover, the Germanic peoples had good soldiers and powerful cavalries.

In its later days, the Roman Empire, had become overstretched militarily. Because of the mentioned migrations, its vast frontiers were under constant attack. This created a sort of cat and mouse game. The Romans had to gather large armies and deploy them to the areas under attack. This exposed other areas because many of its soldiers had been moved to the areas under attack. These areas were, in turn, also attacked. This created a pattern of raids into the parts empire followed by retreat before the Roman army was redeployed to reach the raiders. Over time this increased the strain on the Roman Army.

The initial invasion into Gaul occurred at a time when Roman soldiers were withdrawn from Britain and the frontier of Gaul to fight an attempted invasion of Italy by an Ostrogoth king. The Romans defeated him, but at the price of the mentioned Germanic peoples taking advantage of this to cross the river Rhine and invade Gaul. Because this involved migrations, these invasions were no longer just raids. They were occupations of territories. The number of attackers and invaders was too large for the Roman army to deal with. When the Roman legions withdrew from Britain, the Angles, Saxons, Jutes and Frisians migrated there in waves and eventually took over this island. The Alemanni of southern Germany and the Franks of southern Holland and central Germany took advantage of the original invasion of Gaul to conquer territories there as well.