Say if army B set up a defensive stance so Army A would have to attack, would they just charge? Or would they go to the front lines and probe them and slowly more people get engaged in the fight. Even if A and B attacked each other would they run into each other or would they stop near eachother.
An important thing to consider with this is the composition of the armies. A archer heavy composition could force the enemy to approach immediately, as in the battle of Agincourt. I don't know how a battle between two armies with relatively low numbers of archers would play out though.