Victory conditions can be set at the galaxy setup screen.
There are four ways in which you can win in Galactic Civilizations II:
- Conquest Victory: Wipe out all other major races in order to achieve this. Note that you can achieve this victory without conquering any of the minor races, even if they happen to control more than one planet. Setting alliances aside, a cunning way of doing this is to pay certain stronger civilizations to go to war with the weaker ones in an attempt to weaken the civilizations involved.
- Diplomatic Victory: Form an alliance with all surviving major races in order to win this victory. Your relationship with a potential ally needs to be "close", further, an Alliance can only be offered if both parties involved have the technology "Alliances". There is a hardcoded limit before you can establish a close relationship, it's around ~104 turns. Note that sometimes a relation can jump upwards in 2 steps (from "warm" to "close" in an instant) and this is one way to get to an alliance sooner. But the chance that this happens is abysmal low. This limitation has been integrated to prevent an exploitive "easy"-win by simply buttering the AIs up.
- Influence Victory: Have your civilization's influence dominate at least 75% of the galaxy. When you accomplish this task a message will appear, stating that if you maintain your influence dominance for 10 weeks you will win. You cannot be at war with any of the other major races before this victory is possible. In addition, dominating at least 75% of the galaxy's influence may not be possible without a hold on an already sizable percentage of the galaxy's planets. Maxing out influence-resources is key to this task.
- Technological Victory: There are five technologies at the very far-end of the tech tree that must be researched before being able to win the Technology Victory:
Note that when another rival civilization has researched the penultimate technology (Beyond Mortality, though in TA this might differ for certain civilizations), a warning will be given to the player of this attempt to score a technological victory. Given the exigency of this message, it would be important to annihilate or thwart (perhaps through espionage) that civilization's attempt as soon as possible, but in many cases the warning would arrive too belatedly for the player to do anything about it. In TA, researching prerequisite technologies prior to Technological Victory grants a research bonus (+X%), hence increasing the incentive to research some of the earlier technologies like Deeper Knowledge, which would otherwise be completely useless if the player does not wish to pursue a Technological Victory. In TA 2.20 every techtree holds a unique Technological Victory branch which ends in ultra-brutal bonuses for the win - that is, if you've disabled this victory condition you can still use superior technology to achieve other goals with this research-path.
- Ascension Victory: In the Twilight of the Arnor, controlling a certain number of Ascension crystals for a limited period of time will allow that particular race to ascend and win an Ascension Victory. The maximum number of crystals that are available at anytime (as checked by use of the Map Editor) is 5, though some maps might have fewer. Each crystal a race controls will generate one "Ascension Point" per turn, and victory is achieved once 1000 points have been amassed. Losing a crystal doesn't lose you any points, so one can simply build a new base on top of the crystal and continue trying to ascend.
Some of the scenarios and campaign missions may have alternate victory conditions.
NOTE: It is generally considered to be a score multiplier of 1.0 for a Tech Victory, 1.2 for an Alliance (Diplomatic) Victory, 1.4 for an Influence (Cultural) Victory, and 2.0 for a Conquest (Military) Victory. Also, Ascension Victory results in the same score as a Conquest Victory. This may be of interest to Metaverse players. Source: GalCiv Forum Thread