Battles were fought in much the same way as in the Pre-Marius times, with the exception of the heavier use of artillery. Often before heavy infantry were sent in, a barrage of missile fire from Onagers and Ballistas (ancient artillery) were used to weaken and dishearten the enemy. As the legionnaires approached the enemy and came within thirty yards or so, they would throw a volley or two of pilum that would weaken the enemy before they engaged in hand-to-hand combat. The single lines were replaced with a three to five men line, so that the soldiers could easily rotate to replace fallen or fatigued comrades.
With improved training and uniform gear, there were, however, new formations the cohorts could transform into to meet a new situation. These were prime examples that exemplified the ingenuity and effectiveness of Roman warfare. First and probably the most famous, was the Tortoise, or Testudo. When deployed effectively, the soldiers would raise and interlock their large Scutum rectangular shields so that the entire company became a square box almost completely invulnerable to missle fire and objects dropped from above.
The Wedge was also a very important tactic...