1) Depopulation -- Plagues and low birth rate among Roman citizens led to depopulation in the Empire. In order to combat different times when this occurred, barbarian tribes were actually welcomed into the Empire and encouraged to "set up shop". | 1) Depopulation -- Plagues and low birth rate among Roman citizens led to depopulation in the Empire. In order to combat different times when this occurred, barbarian tribes were actually welcomed into the Empire and encouraged to "set up shop". |