The Roman Senate debates whether or not to accept the Barbarians into Roman society. The senators in favor of the decision feel that accepting Barbarians will make their society grow even stronger. The senators against the decision believe that the Barbarians will still not be loyal to Roman society. Caesar's decision to accept the Barbarians into Rome is made with the expectation that they will be loyal to Rome.
John Green explains some of the decisions of the Roman empire that led to its demise. Most notably, Rome tried to incorporate conquered people into Roman culture, which worked in the early days of the empire, but eventually led to barbarians inside the gates.