A reconstruction of the battle of Pydna, by Peter Connolly, demonstrating how the broken ground disrupted the Macedonian phalanx, allowing the Romans to close with the phalangites and use their superior swordsmanship to good effect.
At various stages in its history the Roman army comprised a militia, citizen soldiers, mercenaries and professional troops, both conscripts and volunteers, although there was no clear linear development. The earliest Roman army will have consisted of the king, his retainers, nobles and whatever clan members could be organized to fight, largely in raids against neighbouring communities. This was a citizen militia habituated to seasonal warfare, in which we may guess that soldiers were motivated by ideas of survival, self-defense and patriotism. By protecting themselves, their families and their smallholdings, they also ensured the survival of the Roman state. Of course, peer pressure will also have been important, as they saw other small farmers in the ranks with them.
As Rome developed politically and militarily, the will of the upper classes usually prevailed in decisions on war and peace, and the government regularly conscripted its citizens, though preferring those who could equip themselves. This, however, did not mean that the Roman people were unwilling soldiers. On the contrary, they were apparently quite belligerent. The levy for Rome’s legionary army around the mid-third century BC suggests that a large proportion of eligible men with property (assidui) were enlisted. Citizens were apparently willing to serve in large numbers at least down to the mid-second century BC. In 225 BC perhaps about 17 per cent of the adult male citizens were in the army, rising to more than 25 per cent at the climax of the war with Hannibal. Furthermore, after 218 BC campaigns were no longer seasonal but could last all year. It is difficult to see how, even with the use of conscription, the senate could have pursued an active foreign policy without a significant measure of popular support and cooperation. The comic playwright Plautus, who was writing between c. 205 and 184 BC, certainly assumes that his audience is familiar with war. He often uses specifically Roman military metaphors, puts a famous battle narrative in a Roman context, and, in a stock feature of his work, the Prologues, commonly ends by wishing the audience well in war.
Roman warfare in this period was often brutal. The troops’ methods for dealing with captured cities caused the Greek historian Polybius, who had military experience, to comment that they were more violent than Hellenistic armies. Indeed, Roman fighting methods and the ferocity of Roman troops apparently intimidated Macedonian soldiers. It has been suggested that the Romans had a pronounced willingness to use violence against alien peoples, and `behaved somewhat more ferociously than most of the other politically advanced peoples of the Mediterranean world’. Perhaps therefore in a violent and warlike society men readily accepted the idea of going into battle to kill those whom they saw as enemies.
Nevertheless, hope of personal gain probably had greatest weight in encouraging men to serve. The introduction of a daily cash allowance in the early fourth century shows that the state itself recognized the need to recompense its soldiers for their service. Soldiers in a victorious army expected to acquire booty and slaves, and this is best illustrated by the increasing generosity of donatives distributed at triumphs. Soldiers might therefore have been attracted by the reputation of a previously successful general, under whose command they could expect victory and profit. Thus Scipio Aemilianus was able to raise 4000 volunteers for the siege of Numantia in 137 BC, relying on his prestige and popularity and clientela connections.
After c. 150 BC enthusiasm for military service declined. The long war in Spain was proving difficult and unpopular; there was little booty, and reports of frequent battles, high casualty rates and the courage of the enemy unnerved many men of military age. Consequently, there were attempts to evade the levy. Moreover, the slave war in Sicily and unprofitable garrison duty in Macedonia created more recruiting problems for the government. Indeed, the property qualification for service had been reduced in 214 and was reduced again in the second century. As men were required to serve for longer or were called up on more occasions, life became harder for small farmers without resources or powerful protectors. Six or more years’ continuous absence from Italy could bring the ruin of a farm, and all this was a disincentive to serve which the government would have to overcome or face a crisis of morale among its soldiers.
In 107 BC the consul C. Marius raised additional forces for the troublesome war in Africa against Jugurtha by accepting as volunteers men who did not possess the requisite amount of property (proletarii). Given the decline in the property qualification in previous years, it is likely that they were not markedly poorer than the kind of soldier recruited in earlier times, but potentially the way was open for the recruitment of more soldiers who had no land and no means of support other than military life. There was now a more mercenary element, in that eventually more soldiers sought a profitable military career, served for longer periods, and tended to be loyal to commanders who were successful and looked after their interests.
In the political turmoil of the late Republic there was no longer a single army of the Roman state, but individual armies serving under competing leaders. About 250,000 Italians, many of whom will have been conscripts, were under arms. Legions were also raised outside Italy from Roman citizens, and often from non-citizens. Julius Caesar enlisted the legion V Alaudae from Transalpine Gaul, while Pompey and Antony, too, were also active in this way. In addition, Caesar employed non-Romans as mercenary troops in a specialist capacity, notably Gallic and German cavalry. Military leaders probably took what they could get in the way of recruits, and the chief incentives to bravery in battle were donatives, booty, and the allure of individual generals whose record promised continued success. Julius Caesar was famous for his close personal relationship with his men, which he had built up over ten years’ successful and lucrative campaigning in Gaul. His troops’ loyalty and devotion were undiminished by military setbacks or harsh conditions, and it was said that Pompey, on seeing the bread made from herbs and grass that Caesar’s army was living on at the siege of Dyrrachium, ordered that it should be hidden from his men in case the enemy’s resolution undermined their own spirit. Soldiers such as these swore their oath of service personally to their commanders, and were in fact virtually mercenaries, supporting their paymaster leaders not because of the compulsion of the law but because of personal inducements, and fighting not against the enemies of Rome but against private adversaries and fellow-citizens. Military service was now a kind of financial package, involving long service in return for regular pay and other benefits. The Roman army therefore did not necessarily have any strong patriotic sentiments or political ideals, or a clear idea of loyalty to the senate or Rome. It had sharpened its skills in warfare against other Romans, and had developed a strong expectation of success. With a professional approach in military preparations, and a tradition of robust leadership from its officers, especially the centurions, it had also developed a strong sense of military community.