You might be hearing different things about Roman battle cries because the use of battle cries by the Roman armies did change over time. During the early imperial period, Roman soldiers were not allowed to make any battle cry or shout until the fighting had already begun. While most of Rome's enemies would be shouting and yelling to try to intimidate their opponents, the Roman soldiers would be entirely silent, even having men behind the formations whose job it was to strike with their spear-butts any soldier who made noise. This had the practical effect of allowing verbal orders to be transmitted smoothly, but it also demonstrated the extreme discipline of the Roman army and projected an aura of calm fortitude. It may have also reinforced the Romans' own ideas of their superiority over their enemies by showing them as less civilised.

From about the fourth century and into the fifth century this began to change. The Roman armies began to use the barritus battle cry, which was of Germanic origin. This may have come into the Roman army through their German recruits. The barritus began from silence and started with a low murmuring that gradually crescendoed into a deafening roar that would peak with the first charge of the infantry. They may have also used their weapons and shield to make more noise, but the association with shields may also come from the historian Tacitus. He uses the word barditus to describe the Germanic battle cries from the first and second century CE and says that they used their shields to reverberate the noise. As time went on the Romans also adopted a number of Christian battle cries and invocations, including Deus nobiscum, 'God is with us', and Adiuta Deus, 'God help us'.