Campaign

The Galactic Civilizations III campaign consisted of three levels that covered the Terran 1st Fleet's return from the Dread Lord's pocket universe up to the reclaiming of Earth from the Drengin.

A tutorial was also included that acted as a prelude to the campaign.

Arcea
At the first campaign level, you start with a fleet of capital ships and a civilian fleet comprised of a transport, a Colony Ship and a Survey Ship. you will have to go through the Drengin blockade on Arcea and take over the planet with your transports. Casualties in your capital ship fleet are to be expected. Throughout this phase, you will be prompted to make several ideological choices. Do Benevolent and/or Pragmatic choices, since those provide a Colony Ship and/or Construction Ships (you will need them early on).

Once that is done, build a shipyard near Hammer and Arcea and spam Colony Ships as described here. Use your Survey fleet to scout for any anomalies while you focus your production on building Colony Ships and Construction Ships. With those you will secure Vega. Your capital ships should clear the immediate area of hostiles while also destroying any mining starbases. Send your own Construction Ships to replace the enemy starbases, therefore increasing your resources and zone of control while reducing theirs. Since their ships are quite tough, it is advised that you first build advanced starbase defenses on any starbase you might have.

If you defeated the Dregin, DL Bradley will tell you to get some rest and wait for orders.

Contingency
At the second campaign level, you are given the resources of Dominion Prime. You then face the Thalan Contingency, who are prophesying against the Terran Crusade. You either go to war against them or unite against the Dregin, who are in the sector. Ally with the Thalan, since they will help you out. You will begin with some capital ships and a civilian fleet, as well as a starbase already on the sector. Colonize the remaining planets or conquer the Dregin occupied planets. Get enough ships to defeat the Dregin.

Eventually, DL Bradley will inform you that the TAS Crusader has made its repairs, and the route to Earth is now open.

Return
At the final campaign level, you head a massive navy, consisting of capital ships and a civilian fleet, to liberate Earth from its Precursor Shield and end the Dregin blockade. You have the option of allying yourself with the Altarians, the Iridium, and the Krynn. Ally with all of them until one of them declares war on you (particularly the Krynn). You also have the option to destroy the Yor, as they helped out the Dregin.

Construct strong ships, and send them and the Crusader against the Stepping Stones (planets whose paths lead to Earth). Once you capture Mars, the Dregin will promise that they will return, and DL Bradley will tell you to get the Crusader to ending the Precursor Shield once and for all. Ships that humanity on Earth were building are then released into space, beginning the Terran Crusade, an event long prophecied by the Thalan.