During its time, the Roman military was one of the strongest in the world. By the 3rd Century CE, it had helped the Roman Empire conquer most of the known world. It had defeated a number of strong enemies, such as the Carthaginians. However, it was unable to fend off the barbarian tribes that eventually brought about the end of the empire. Let's look at some of the strengths and weaknesses of the Roman military.

Strengths

One of the biggest advantages that the Roman military had was its size. Recruitment during the period of the Punic Wars and the early Imperial period was massive. Italy tended to supply the elite soldiers of the Praetorian Guard, but the colonies and Romanized provinces supplied the rank and file of the army. In many of its conquests, the Romans were able to put a large number of soldiers in the field and outnumber their enemy.

Roman soldiers were also very experienced. Rome employed a professional army where soldiers served for decades. This meant that they were well trained and battle-hardened. Unlike civilian armies, Roman soldiers were ready to fight on the battlefield without the need to spend time training and mobilizing.

Being a professional fighting force, the Roman army was able to employ advanced battle tactics. The legion formation required the training and discipline of professional soldiers. This tight and coordinated battle technique was easily able to defeat enemy armies that were unused to such coordinated fighting.

The versatility of the weapons of the Roman army was another strength. They were able to employ the latest in military technology to their advantage. Heavy weapons such as ballistas and trebuchets were useful in sieges. They knew how to use long-range javelins and short gladiī depending on what the battle plan called for.

Weakness

The Roman army was never really able to develop its cavalry. The Roman cavalry remained a relatively weak auxiliary fighting force throughout its history. It was never able to contend with the cavalry of their Persian enemies.

At various times throughout the history of Rome, military leaders were politicians and aristocrats looking to add a feather to their cap. They were not always seasoned and knowledgeable military commanders. These amateur commanders stumbled into a number of embarrassing defeats. Most notable was Varus, who lost three entire legions fighting the German tribes in 9CE.

By the 4th and 5th Centuries, recruitment had become a problem. The army just was not big enough to defend such a large empire. To fill the gap the Romans began using more barbarian mercenaries in their ranks. This coupled with the declining quality of equipment greatly weakened the Roman military by the empire's end.