We often forget that the Roman army was really clever because we only remember that Rome fell pretty fast late in their reign. However, Rome was so powerful in its day that it would be able to take over anybody at any time. In fact, Rome was so powerful that it's in the Bible. The Roman army was clever, and they even did things that we still do today if you think about it for just a moment.
We expect everyone today to get an engineering degree when they go to the military academies, and that's because the Romans were builders. They were able to build more than anybody else, and they were often building things that made it much easier for them to win battles against other armies. Yes, they were able to use techniques like the Phalanx that they borrowed from the Greeks, but they were also able to build up things that made life easier.
The Romans built many of the first roads, and they used those roads to get on top of other nations that didn't have such technology. You see, another army would've to trek across the wilderness for days to fight a battle, but the Romans would just walk up a road to get to where they wanted to go. This made battling easier.
Rome was able to make its own catapults, and the nation was able to use these catapults to defeat their enemies. The same thing is true when they were making other kinds of weapons that made the army stronger. They had the strongest steel to make their weapons, and they were able to make sturdier weapons that'd last longer in battle.
The Romans borrowed the idea of mandatory schooling from the Greeks, and their people were so smart that they could make better decisions on the battlefield. People who were fighting against the Romans didn't have the necessary intelligence to keep up with the Roman army, and the Romans were able to use new military tactics that made them hard to defeat. These tactics are used to this day, and they weren't afraid to take risks.
They Were Larger
The Roman army was smart enough to scare its opponents before it even got started. The army knew that it could frighten many of its opponents by simply setting up in a place where it'd be easy to see how outnumbered the competition was, and this is going to make it much easier for the Romans to get out of battles without any casualties.
The idea behind the Roman army was wisdom, and that wisdom was going to be used every battle. They were smarter, built all the best weapons, had roads to walk on and they were willing to overwhelm their opponents with the numbers that they knew they had. Combine that with strong spears and the phalanx, and the Romans are arguably the best army that had ever roamed the Earth.