Final answer:
Noncitizens could earn their citizenship in the early Empire by joining the army.
Step-by-step explanation:
In the early Empire, noncitizens could earn their citizenship by joining the army. This was known as the Roman military oath, which promised citizenship at the end of military service. By serving in the Roman army, noncitizens would have the opportunity to gain Roman citizenship and all the rights and privileges that came with it.
Learn more about Roman citizenship