In a typical battle both sides will skirmish with ranged units to reduce the firepower of the opposing side. If one side takes too many ranged units, the answer to that is to attack with melee units. If one side takes too many melee units, the answer to that is to skirmish with ranged units as much as possible. How much is too much ranged or melee has to be determined by experience. Through experience, players will find an optimum mixture of ranged and melee units which means that neither of the two options for attacking is viable. That is you can't win the skirmish against your opponent decisively, and you can't charge successfully. A team game offers another attacking strategy which is to send more units against one of the opponents than he can handle.
In a basic 2v2 situation, suppose you have C and D attackers and X and Y defenders:
If C attacks X, D can assist C and delay attacking Y:
If Y moves to assist X, then D should attack Y. It's important that D's main army be close enough to Y to effectively counter Y's move. The D player has to control the units that are assisting the attack on X, and also keep an eye on Y for any sign of movement.
In this case, Z effectively takes responsibility for one of the B units and Y for one of the C units. X and Y have to watch for additional moves by A and B, and react to them. If A and B make a major move to the defender's right, Y should not consider A to be his opponent because that will result in Z being doubled by B and C. Even if X and Y double and rout A, that will not compensate for all of Z + the X and Y units on the right being routed.
Where rather than mirrorring the move of the opposing team, XYZ team will try to overwhelm army A before Z gets overwhelmed, relying on local superiority against A while at the same time Z stays backwards avoiding combat so that it denies the local superiority team ABC local has against Z.
In this situation, as it will take longer for the 'extra' forces from ABC to travel towards Z than it does for the 'extra' forces from XYZ, team XYZ should be able to overwhelm A before Z gets overwhelmed.
Yes, but there has to be a weakness in the center that you can take advantage of to force a breakthrough.
Yea. I had times when I broke the middle, but my allies were were to busy with the flanks and ran into the problems and could not spare troops to help me, so I could not outflank them, the middle reform with help of their allies, and smash though me.
Just need to find that weakness, beat though it, and follow up it fast so the allies of the middle person do not have time to help him fight you off.