Compared to the Warrior of the previous age, the Legionnaire gains +2 attack, +3 defense, and gains attack and defense bonuses against light units and on plains.
It has the highest defense among the Iron Age units but has subpar attack power and slow speed. It has a defense bonus on plains and a combat bonus against light units.
Legionnaires are effective against both the Soldier and the Mounted Warrior, but are vulnerable to the Ballista and Archer, as both have a combat bonus against Legionnaires. Due to its slow speed, it is usually killed without doing any damage when encountering an army with several ranged units and artillery units. Therefore, legionnaires should be used to counter melee oriented armies, where their high defense can allow them to tank hits.
After the implementation of the Marian Reforms, in 107 BC, the integral structure of the Roman army was changed to a more "efficient" one, as a reaction to the structural and logistical stagnation of the "Pre-Marius" forces during the time of the Roman republic. One of the key military differences between the two was that the traditional maniple, the original base formation of the roman forces made up of militia levies, was changed to the cohort, a military formation comprised of professional soldiers known as Legionnaires. Unlike in the Pre-Marius times, Legionnaires were supplied their gear by the state and enjoyed the opportunity of claiming spoils of war at an individual level, the eligibility requirements were also lessened to allow a further array of citizens to join the ranks. The equipment of the Legionnaire was relatively simple, cheap and effective. Beyond their tunic, Legionnaires were cladded with a fairly effective set of armour, known as lorica which could vary from the Lorica Segmentata, made from sheets of metal and being the most widespread set of armour. Lorica Hamata, a type of chainmail that could be worn below the other and the Lorica Squamata, a rare type comprised of metal scales. The helmet, known as Galea or the Gallic Imperial helmet, provided a good amount of protection to the soldier's head, neck and face and didn't block the ears which allowed the soldier to hear properly during battle. Crests in the helmets were used to distinguish ranks, especially during the early days of the empire. Legionnaires used the Gladius as their main weapon, a dagger like short sword used for thrusting and piercing. They also used the Pillum, a heavy javelin that could be hurled to provoke a significant amount of damage to an enemy, because of the metallic composition of the tip of this weapon it would often bend upon impact making it unusable to the enemy and ruining the integrity of any shields it might've hit. Lastly, legionnaires relied on their Scutum for protection, the iconic oblong large shield that was used in conjuction with the ones from other soldiers to make impressive defensive formations, it was also used as a weapon given its mass and size.