Weapons
There were many differences in the type of weapons Rome and the Byzantines used. Roman weapons were more directed and made to rush down the enemy. The Byzantines used longer range weapons and stayed away from the enemy. The Gladius is the ionic short sword of the Roman empire. During the Byzantine rule, the short sword was dropped and longer sword the Spathion was being used more. The Roman used more spears and threw larger projectiles at there enemies such as the pilum and the hasta as their mid to long range weapons. The Byzantines used arrows which traveled longer distances instead, and they stayed away from their enemies from a farther distance. During the Byzantines empire, they were able to figure out how to use fire as a weapon. No one was close to having a destructive weapon such as Greek fire at this time. By having Greek fire; made the Byzantines one of the most advance civilizations for their time. The Byzantine also decided to used cavalry while using their advance weapons. The advancements from Rome to the Byzantine empire was a great change for weaponry and warfare.
Military Tactics
Military Tactics became a lot more complex during the Byzantine rule. Rome an effective tactic for their time. Consistently having new fresh soldiers fight the enemy a group a time explains how they were able to be the empire they were. The Byzantine had improved weapons and more advanced tactics once cavalry were involved. The Byzantines had two groups of people different train. Some became spear-men/swordsmen and other became archers. The Roman only train their soldiers to be swordsman and javelin throwers. Having a mix of heavy infantry and archers proves to be an effective strategy. When the Byzantines added Kataphraktoi, armored horses and light cavalry mad the army of the Byzantines more diverse and more suitable to take on a war. The way they train the soldiers and horses specifically to their own types of weapons would be what warfare is today. The Byzantines also avoided face to face combat and flanked instead. This saved more men. Warfare had a significant change between the Roman empire and the Byzantine empire.
Defenses
The defenses of Roman and Byzantines empires are greatly different. Rome was a giant empire and protection it wouldn't be easy. They did mange to build a few walls such as Hadrian's Wall. Rome did have good walls which did have some protection form their enemies. The Byzantines just had a better walls than Rome. The walls of Constantinople were amazing in their design. Having many stages and different types of walls keep Constantinople safe for the Byzantines for 20 invasions. Warfare had a significant change during this time in history with the Byzantines defenses.