This mission would be very difficult if not for the AI's stupidity. The map is divided into two parts, connected with two bridges in the middle (1). The enemy will thoughtlessly send his troops through these bridges, not realizing that these attack are all too easy to defend. You've got a lot of resources on your part of the map so just secure the bridges and expand until you've got a gigantic army that won't have any problem cutting the enemy where he stands (3).
While the main quest is fairly simple here, a side-quest can prove to be troublesome. You have to escort 7 transports coming from either of the (2)-points into your base. The enemy will send his flyers to bring them down, so if you hope to complete this one, you should emphasize on building air forces. Keep them in the central part of the map and send them where they are needed (meaning - where the transport is coming from). And be quick about it, you have to keep up with the pace. If you manage to save all 7 transports, you'll get 2 powerful units: a Death Sphere and a Storm Disk (aren't really worth the trouble if you ask me, but hey, a side-quest's a side-quest).