1. The professional Roman army: The Roman army was one of the most powerful and disciplined armies in the ancient world. It was well-organized, well-trained, and well-equipped. The army was able to maintain order within the empire and defend its borders from external threats.
2. The Roman road system: The Roman road system was one of the most extensive and well-built road systems in the ancient world. It allowed for easy transportation of goods and people, which helped to promote trade and economic development. The roads also made it easier for the Roman army to move quickly and efficiently to any part of the empire.
3. The Roman legal system: The Roman legal system was one of the most advanced and sophisticated legal systems in the ancient world. It was based on the principles of justice and equality under the law. The legal system helped to maintain order and stability within the empire and to protect the rights of Roman citizens.