Patricia Southern quotes ancient historians Livy and Dionysius in saying that the 'phalanx consisted of 3,000 infantry and 300 cavalries'. This was due to Greek influence in Italy 'by way of their colonies'. Until the Roman military disaster of 390 BC at the Battle of the Allia, Rome's army was organized similarly to the Greek phalanx. Any man 'from ages 16–46 was selected by ballot' and assigned to a legion. The bulk of the army consisted of citizens, who could not choose the legion to which they were allocated.

The first legion was seen as the most prestigious. At first, there were only four Roman legions numbered 'I' to 'IIII' (with the fourth being written as such and not 'IV'). The term legion is derived from the Latin word legio, which ultimately means draft or levy. The commanding position of the army was given to the consuls, 'who were charged singly and jointly to take care to preserve the Republic from danger'. However, from about 508 BC Rome no longer had a king. Until the establishment of the Roman Republic and the office of consul, the king assumed the role of commander-in-chief. When the army of Rome would be brought together on the Campus Martius it was called the Comitia Curiata. Moreover, the commanding authority during the regal period was the king. The infantry ranks were filled with the lower classes while the cavalry was left to the patricians because the wealthier could afford horses. They would not serve in the army unless it were an emergency. Any poorer citizen called capite censi would have no weapons. The fifth class would only be a screening force. The fourth class had a shield and a spear. The third class could only afford to have a shield, a sword, and a spear. The second class had greaves, a shield, a sword, and a spear. The first class could afford to have a cuirass, greaves, a shield, a sword, and a spear. Each of which would have different roles in the military. These would divide the population into five classes. King Servius of Rome would institute the Servian reforms.

The Latins, Sabines, and Etruscans under the Roman state would each provide an extra 1,000 soldiers and 100 cavalrymen. The army consisted of 3,000 infantrymen and 300 cavalrymen, all of which were Equites. The early Roman army was based on an annual levy. During this period, when warfare chiefly consisted of small-scale plundering raids, it has been suggested that the army followed Etruscan or Greek models of organization and equipment. The early Roman army was the armed forces of the Roman Kingdom and of the early Roman Republic.

Rise of kingdoms commanders