The correct answer is - pull factors.
The increased freedom and much more employment opportunities in the United States can be considered as pull factors. They can be considered as pull factors because they are big reasons why people from all around the world got attracted to the idea of migrating to the United States, as they saw a nice chance to prosper and have a better life. Most of the countries were still struggling with the freedom issues, and the employment opportunities were either very limited, or badly payed, so no wonder that pople wanted to move in the United States.
The main advantage which the Germanic tribes had in their conflict against the Roman Empire at the time during the 3rdr and 5th century was that they were very motivated to defend their own lands which were invaded by the Romans. They also knew the terrain and felt comfortable being there.
Luckily, I had remembered this type of question before, next time please states how and what you want the answer to be like.
33° North
44° East
