Answer
They needed to be stronger for deadly fights
Step-by-step explanation
Roman military units of the period consisted of units of citizen infantry known as legions .as well as non-legionary allied troops known as auxilia. The latter were most commonly called upon to provide light infantry or cavalry support. The Roman Empire was powerful, due to its strong military tactics and their military policies helped to expand the empire. The soldiers were highly trained in the latest tactics of war and were well equipped with the weapons of war.
According to . Vegetius, who was a writer of the Later Roman Empire the changes in Roman military armor and training techniques were to strengthen the force for the deadly fights.