Your very first objective in this map, is to get your reinforcements to the fort in the middle. Do so quickly, especially artillery, but keep some of your tanks and soldiers ready for the next four objectives.

These four objectives are more or less the same: you need to secure a specific area to stop enemy/AI units from spawning and repeatedly raiding the fort. It does happen that the enemy/AI units spawn one last time, even if you have occupied the area, so beware of that. You win when all five objectives have been completed.