How to complete mission 3-32?

This one can be quite tricky and you will need a strong infantry to do this, get them close to the turrets and activate bunkers so they come under fire, then bring in the rest of you units to take out the armies and turrets, do this for all three turrets.

You can take your time as there is no time limit for this mission. Watch out for reinforcements before you move onto the next turret.