Descent: FreeSpace - The Great War is a space simulation computer game series developed by Volition Inc., one of the two companies (along with Outrage Entertainment) that formed when Parallax Software, the creators of Descent, split. For contractual reasons the game was called Conflict: FreeSpace - The Great War in Europe. After THQ acquired Volition Inc., the source code for the game was released to the fan community and the FreeSpace engine has continued to develop under the FreeSpace Source Code Project.

FreeSpace 2 takes place 32 years after the events of Descent: FreeSpace. The alliance between the Terrans and Vasudans is sealed with the foundation of the Galactic Terran-Vasudan Alliance (GTVA). The GTVA campaign in this game is threefold. Their first priority was in stopping the Neo-Terran Front (NTF) led by Admiral Aken Bosch. Bosch, a veteran of the Galactic Terran Intelligence (GTI), united a group of rogue Terrans under the banner of hatred of Vasudans. Initially, he threatened to destabilize the Alliance and destroy the Vasudan race. The second priority was the discovery of the Knossos Device, a massive, ring-shaped device believed to have been constructed by the Ancients. In essence, the Knossos appeared to be an artificial portal generator. This obviously interested the Terrans, who were still searching for a way to return to their homeworld Earth. The third, and most dangerous, was the return of the Shivans. This time, the Shivans have a fearsome new array of ships, including the SJ Sathanas that is over 5.5 kilometers in length.

During the course of the campaign, the player learns about the truth behind the Neo-Terran Front and the nature of the Knossos Device. The NTF insurgency is quelled near the beginning of the campaign when the Knossos Device is activated; this opens access to a nebula that is discovered to be filled with Shivan forces. Inside this nebula is discovered a second Knossos portal. As a result of this second portal, the eventual retreat and destruction of the first portal is not enough to stop a second Shivan incursion, and as hopes for victory slowly disappear, humanity takes desperate measures in order to secure its survival. The most daring of these include the introduction of the GTVA Colossus, a 6 kilometre long juggernaut and the use of the GTD Bastion (one of the player's base of operations from the original game) loaded with meson bombs detonated in the threshold of a jump node in order to seal it in the same manner as the Lucifers destruction sealed off the Sol jump node at the end of the first war.

Despite these desperate measures, the Shivans continue their assault and show no signs of stopping. The Colossus plays an integral role in many of the GTVA campaigns, especially the quelling of the NTF insurgency, but it meets its match in the Shivan SJ Sathanas-class juggernaught. Though the first Sathanas is destroyed, the Shivans unleash a dozen more of these juggernauts. The inevitable destruction of the Colossus causes Alliance morale to plummet, as the Shivans grow closer and closer to finishing what they started 32 years before. In a cutscene near the end of the game, the player is shown the last recorded log entry of Admiral Aken Bosch. By this point in the game, it is already known that Bosch has been attempting to make first contact with the Shivan forces (up until then, contact had never been successfully made with Shivan forces.) While listening to the log entry, it is revealed that Bosch was apparently successful in his attempts. Furthermore, he and several of his crew were actually brought on-board a Shivan transport for reasons unknown (most of its crew had been slain by the time Bosch's flagship was discovered). It is never revealed whether the Shivans are actually interested in contact with the Terrans, or if their communications with Bosch were further attempts to destroy the Terrans.

In the final mission of FreeSpace 2, the player is tasked with evacuating Terran civilian and military personnel from the Capella system, where the Shivans were inexplicably congregating. At least eighty Shivan Sathanas-class juggernauts surrounded the Capella sun. In the final minute of the mission, the Capella star goes supernova and the player is presented with a choice: stay behind to help the last civilians escape (which will invariably result in the player's death from the blast of the sun), or flee to the jump node and escape. Both options are acceptable, and the game will be completed either way, with different final cutscenes for each.

The final cutscene displays the Sathanas fleet in the process of detonating the Capella star. Just before it goes supernova, most of the Juggernaut fleet enters subspace and flee to an unknown location, with the remaining Juggernauts going completely dark just before the star explodes. Why the Shivans caused the supernova is one of the major questions still on fans' minds.

However, a hint at the reason for detonating the sun is given in one of the two ending cutscenes. If the player escapes the supernova on the last mission, in the following cutscene Admiral Petrarch hypothesizes that the Shivans may be exiles themselves, and that the supernova is a long-range subspace gate through which the Shivans are returning to their homeworld, which would explain why many of the Sathanas Juggernauts entered subspace soon before the Capella star exploded. Such an exodus of the Shivans may be considered an effective end to the storyline.

The Shivans (named after the Hindu god of destruction and regeneration Shiva) are an ancient, destructive race that has exterminated countless spacefaring races and recently fought two destructive wars against the Terrans and Vasudans. It has been confirmed that Shivans are in fact xenocidal. Shivans have a black exoskeleton, five legs, compound eyes, and are apparently some form of cybernetic organism, with both organic and inorganic components including an integrated plasma weapon. They are physically extremely strong and well adapted to a microgravity environment, possibly having evolved in it. The typical Shivan specimen is roughly 4m to 5m long and its height varies between 2.5 and 3.5m depending on its posture. It is theorised that the integral plasma cannon, inorganic materials, and cybernetic components can be explained by the use of an artificial exoskeleton of sorts (Descent: FreeSpace, Disc 2, the video featuring the boarding team).

Only a handful of Shivans have ever been captured, and all research on live specimens ended with the rebellion of the intelligence branch of the GTA at the close of the Great War. The results of these studies remain highly classified.

In Descent:Freespace the narrator (an Ancient) speculates that the Shivans are closely tied with subspace; they apparently are native to subspace, and take notice of any species that travels through it, acting to exterminate them. At the end of Descent: FreeSpace, it is theorized that the Shivans are the Galaxy's immune system, a premise similar to that in Starflight 2. They appear and exterminate any species that develops subspace technology. By doing so, they prevent any one species from spreading across the entire galaxy and dominating all other races. It is theorized that humans would never have developed if not for the Shivans, because the Ancients would have been allowed to spread and eventually conquer Earth. Likewise, the Ancients would not have been able to develop, as they would have been conquered by the races that came before them.

At the end of FreeSpace 2 a vast Shivan fleet destroys the Capella system's sun for unknown reasons. It is theorized that Shivans are denizens of another universe and were trying to produce some type of subspace portal in an effort to get home.