The ancient Roman army became the archetypal model of military success, using some well established principles and adapting capabilities for different terrains and needs. Initially based on the Phalanx they soon evolved the units and armament for more flexible strategies.
The ancient Roman army is known for it’s extensive successes over time, different geographies, terrains and types of enemies.
The early Roman army was based on conscription. Soldiers were therefore the common Roman citizens who took on a role based on their personal wealth. The richer members of society could afford horse and weapons and would hence tend to become Roman knights (equites) part of the cavalry whilst the poorer plebeians would fall into the infantry. The early cavalry was usually small and limited to some 300 men. War tended to be seasonal also allowing for the soldiers to return to their homes and farms to tend to their harvests.
Early battle strategy was typical of the times, also learned from neighbouring nations like the Etruscans and Greeks. The Phalanx was popular, based on many foot soldiers with interlocking shields and spears. The Romans developed these formations into more agile smaller units such as the “manipuli” more suited to uneven ground and capable of taking advantage of breaks in the Phalanx formation.
During the Roman republic, general Marius transformed the Roman army by introducing conscription and allowing soldiers a regular pay and long term career. This meant that the army was now ready to go and highly trained. It no longer required the delays of conscription and retraining every time it was required to come into action.
An unexpected side effect of Marius’ reforms was that the army became more directly attached to the individual generals.
The army was typically split into three fronts of increasingly experienced forces. The Hastati, holding spears, were placed at the front in a tight formation. Behind them the Principes were in looser formation. And thirdly the Triarii in the loosest of formations, able to receive into their midst the fall back from those in front of them.
The lightest soldiers were bowmen and slingers and were not necessarily part of the main body of the army formation. They might be set in front of the hastati to initiate the combat in a flexible way or spread across the hastati or placed in the wings.
This basic structure allowed the army to rally up to three times. Each wave provided the room and agility required to most effectively use its own set of weapons.
The cavalry would be typically posted at the wings and could fight on horseback or foot as necessary.
The general would typically be at the centre of the army, possibly between Pricipes and Triarii. He would decide where to place his commanders – the Legati and Tribunes, for example to lead certain critical parts of the battle such as the wings or even by his side. Centurions were split into ranks, the ‘primipili’ first among them, decided how their centuries would be disposed .
This basic outline of the Roman armies line-up could be modified according to need and specific situations to create a variety of shapes and formations such as wedges, circles, various rectangular alternatives or even saw shapes.
The ancient Roman army formations could be set to meet varying needs of terrain and enemy strategy, very similar to a game of paper-stone-scissors where the right formation could counter-act that of the opponent army.