German migration and settlement in the east is frequently thought to be the main phase of the historic struggle between Germans and Slavs. But national sentiment and national direction were lacking on both sides. Whatever planned political direction was found among the Germans was exercised by individual princes, both secular and ecclesiastical, by cities, and by the German nobility. Their policies would have been to no avail had they not had strong popular support. The dynamic force in the eastward German migration was the fast-growing population of Germany and its hunger for new land.
Overpopulation is a relative term.
The number of people who can live in a square mile depends not only on the fertility of the soil but also on the technological skill of the people. Moreover, the industrial and commercial opportunities of any region and age have to be taken into consideration. The Rhinelanders were next, but eventually people from every German stem contributed to the migration. The economic motive provided the common force behind it. This is not to deny that antagonism between Germans and Slavs existed.