How was a typical battle

DEPLOYMENT:
Normally Cesar has troops in three lines (triplex acies), namely:

 On the wings on either side of the formation was placed the cavalry, and in front of the first line were deployed light infantry and archers. The main purpose of the cavalry was to protect the rest of the army from the danger of the encirclement. In fact, when Caesar thought that not be enough protection, he built the fortifications. In 3 or 4 hours the army was able to build a square of 660 m on each side surrounded by a one meter deep moat and an embankment on which was built a fence, more or less complex.

But what happened in the battle?
Initially, the shooters and the light infantry hurled projectiles towards the enemy advancing and then retired behind the legionnaires. The legionaries hurled their javelins (the pila) made ​​in such a way as to bend, but not break once impacted against enemy shields, making them ineffective. In this way, the first line of the first cohort were often engaged in combat with enemies without shields. In the melee the legionaries advancing semi-squatting, pushing and hitting the enemy with their shield and hitting with the sword from above the shield. While the front line fighting the other continued to throw its javelins. To a signal of a trumpet, the first lines widened to allow the forward pass of the back lines, so as to have a constant turnover of forces.