Answer:
The movement of the Germanic tribes shown in Document 1 was primarily caused by the push of the Huns from Central Asia. The Huns' movement towards Europe caused a domino effect of migrations as various Germanic tribes, such as the Visigoths, Vandals, Angles, Saxons, and Franks, were displaced and forced to migrate in search of new territories to settle. The western Roman Empire's weakened state and inability to defend its borders also contributed to the ease with which these tribes were able to migrate into the region. The map highlights the various routes and directions of these migrations, which ultimately led to the establishment of new kingdoms and states in Europe.