In the early days of the Roman Republic, military tactics were influenced by the methods used by the successful Greek Army. The combat formation used by the Greeks and Romans was called the phalanx. This involved the soldiers standing side by side in ranks. Just before contact with the enemy, the soldiers moved in very close together so that each man's shield helped to protect the man on his left.
With only about three feet between the rows of soldiers, the Romans would move towards the enemy. The phalanx was a very difficult barrier to break through. If a man in the front was killed, he was replaced by the man behind. The shields would not only be used to protect the soldiers, but to push the enemy soldiers to the ground or to make them break ranks.
The phalanx formation was used for hundreds of years. However it proved inadequate against lightly-armed, fast-moving cavalry. The Roman Army therefore introduced a new system that involved the infantry being organised into four groups: velites, hastati, principes and triarii.
The velites were young and inexperienced soldiers. They were at the front and their main task was to make the early attacks on the enemy. When they were recalled, the velites passed through the open ranks and went to the back. The front rank was now made up of the hastati. When they were about 35 metres from the enemy they threw their javelins (pill). Drawing their swords, they now charged the enemy. Behind them, the rest of the Roman Army threw their javelins over the heads of the advancing hastati.
If the charge proved unsuccessful, the hastati withdrew and re-formed behind the rest of the army. It was now the turn of the principes to attack. The principes were the best soldiers that the Roman army had available. The enemy, exhausted by the previous attacks, now had to face fresh and experienced soldiers and, it was usually at this point that they broke formation and ran away. However, if the principes were unsuccessful, the last group, the triarii, would be brought forward.
When the enemy retreated, the Roman cavalry would be called into action. Up until this point the main function of the cavalry was to make sure the infantry were not outflanked by the enemy. When the enemy fled from the battlefield, the cavalry hunted them down. The Romans were never very good on horseback and the cavalry was often made up of meroenaries from Gaul and Africa.
The Romans always gave careful consideration to where battles should be fought. They preferred to be in a higher position than the enemy. If the enemy relied heavily on their cavalry, the Romans tried to arrange it that the battle took place on rough ground. The Roman commanders also liked to ensure that the sun and the wind were behind their soldiers.
The Romans were extremely good at siege tactics. Roman engineers developed several different devices that could throw stones and javelins long distances. The most important of these were the catapulta, ballista and onager.
If the enemy refused to surrender, the Romans also had a wide variety of weapons to break through the walls of a town. Working parties would be sent in to fill in the defensive ditches that usually surrounded the walls. The men used mantlets (wooden sheds, about 5 metres long and 3 metres wide, mounted on wheels) to protect them while doing this work. To draw the fire away from these men, large timber towers on wheels were pushed towards the walls, from which archers would fire on the enemy soldiers.
Once the ditch had been filled in, the Romans would use a ram to try and break down the wall. This weapon was a large wooden beam with a heavy iron head. The end of the beam, which was in the shape of a ram's head, would be constantly hammered against the wall until a hole appeared. Then the Romans would use another beam, this time with a iron hook at the end, to drag out the stones from the breached wall.
The soldiers would now attempt to get through the wall. To protect themselves against attack from above, the men sometimes advanced in a tightly formed group with their heads covered by their shields. Understandably, this method of attack became known as the tortoise.
Siege towers would also be used to get men inside the walls. These towers would have fixed bridges at the top to enable the men to climb onto the walls. The Romans also had a type of crane that could swing small groups of men over enemy defences.