The Fornax War refers to three separate times in history. The Expeditionary War, a period of over 100 years where a fleet of Diunity ships pillaged various areas in the galaxy, the start of The Pestilence, a rogue Von Neumann Probe accidentally created and released by the Diunity, and the War of Revenge, the CoB's retaliation for the destruction in the Milky Way.
The War ended in 14457 CE, when the Diunity proposed a peace treaty in which the two nations would unite as a way to appease the angry populace of the Milky Way.
The Diunity of Fornax was a nation predominantly made up of a race called the Molkor. This nation was older than the CoB by around ten thousand years, meaning it had far more advanced technology. The Molkor were naturally a very aggressive race, but this attitude mostly died down by the time they became a Kardashev III civilization. However, a more fundamentalist movement challenged the idea that this aggressive nature was a bad thing. Even though only a thousandth of the population came to alter themselves to this more "natural" state, this still had major implications for the future of the civilization.
This lead to a need for a larger police force, more ships, and also a shift towards a more capitalistic society in general. This culminated in the creation of the The Spiral Expeditionary Force (SEF), a collection of several million police craft repurposed into military vehicles for the expansion into the Milky Way and other nearby galaxies. The large difference in technology meant that even ships used for domestic law enforcement were superior to even the most advanced military craft in the Confederacy of Borealis.
The first mission of the SEF was the conquest or subjugation of the Sextans I galaxy, which was a small nearby Dwarf Galaxy also orbiting the Milky Way. This proved to be entirely successful, and the galaxy came under the control of the Diunity in 12004 CE.
The Milky Way
At the time, the CoB, the largest of the Milky Way nations, broke away from local alliances and international peacekeeping organizations after a populist movement in the nation. This left several dozen early to mid type II civilizations without their strongest ally. Most governments, however, simply assumed that the universe ended at the edge of the galaxy. To put it another way, they assumed that intergalactic threats were merely speculation and wouldn't actually come into play in the near future.
Course of the War
Attack on Cygnus Site 12
The Spiral Expeditionary Force first entered the Milky Way on July 30th, 13894. After several months of surveying, they stumbled upon a military base controlled by the Confederacy. The base, named Cygnus Site 12, was designed to defend a rich Strange Matter deposit from outside threats, which were mostly pirates.
As per protocol, the base signaled the Fleet with the galactic standard signal for "You are trespassing, leave the area" and the distance the fleet would need to travel in binary. Since the Diunity had no previous contact with any civilization in the Milky Way, these signals were unable to be interpreted. The commander of the fleet decided to treat this base like all of the others they came across, and fired upon it. Even though the Fleet was outnumbered ten to one, its advanced technology allowed it to entirely destroy the base within days.
This is what is often considered as the start of the Fornax War. Although, many historians argue that the conflict started when the Molkor first attacked the Sextans I galaxy.
After several weeks time, the fleet found a mining facility and destroyed it. Later on, the fleet decided to destroy a fairly new colony world. They decided not to take hostages as they didn't have enough room on their ships. Panic spread through the CoB and nearby nations as seemingly random bases, facilities, and worlds were destroyed. The fleet caused the most amount of problems for the owners of these facilities which were mostly corporations or wealthy individuals.
When the Battle of Halfred occurred, ending up in the sterilization of an important colony of Halfred Corporation (a planet named Bisydu). This event caused these corporations to begin pressuring the government to handle this issue. Eventually, they got their way and the government started putting far more effort into the issue than as if it were mere pirates. Large bounties were placed on this fleet (which they still had no idea was from the Fornax Galaxy), the CoB increased the number of ships in service, and began dispatching millions of ships to look for this fleet.
When they finally found the fleet, hundreds of thousands of worlds were already raided or destroyed, quadrillions of C-Units of damages were recorded, and almost one billion lives were lost. Immediately, several billion ships from the CoB engaged the fleet, while normally this would have been enough to utterly destroy any enemy, the SEF proved to be more of a threat than anything in the Milky Way.
During these battles, however, it was not as though the SEF was indestructible, far from it. They would often sustain heavy damages in the most intense battles. This is the reason for why they carried Von Neumann Probes meant to gather materials from the galaxy and return the materials to the ships. These probes would often only go as far as to disassemble asteroids for materials.
The SEF's leave
After more than a century of continual battles in which the SEF would easily defend itself from the various attacks by the CoB and nearby nations, it returned to the Fornax Galaxy to resupply, update their weapons, and mostly for the commander to gloat about all of the battles they won. This action, however, left behind many hundreds of the Von Neumann probes in the Milky Way.
They simply carried on gathering materials and making more of themselves. Before, they would only gather enough materials to replace their numbers since they deposited most of it at the SEF carrier ship. Without the SEF though, the probes were able to quadruple their population within a year. Within the space of a decade, their numbers grew to over a trillion, and by the time the SEF came back 100 years after leaving in 14009, they outnumbered every sapient individual in the Milky Way.
When the SEF finally came back, the probes were so numerous that their algorithms were unable to queue the depositing of materials effectively. The SEF ended up having to fire on their own probes to clear a path. Even after destroying almost a billion, they hardly made a dent in their numbers. Days later, the algorithm broke down to the point at which they started harvesting the SEF ships themselves. The probes even started cannibalizing each other.
On January 4th, 14099, The Pestilence came to be out of these probes. All at once, the several quadrillion probes scattered in all directions, harvesting asteroids, small moons, ships, and space stations as well as severely damaging infrastructure. The entire galaxy had to contain these probes, or the entire Local Group would end up destroyed (many experts say that the entire observable universe would end up destroyed, but this is contested).
These probes soon began making interstellar travel in denser areas almost impossible, as any and all ships not protected by a thick atmosphere would end up destroyed. Gas giants were especially susceptible to The Pestilence, not because they were being harvested, but because of their many moons and rings which provided ample materials for the probes.
Every single Kardashev II civilization near and around the Milky Way suddenly had to deal with the threat of losing the ability to travel in space at all. Nations not even involved in the SEF's raids started having to exterminate these probes. The scale of destruction put the SEF raids to shame, there were more than a quadrillion casualties over the course of the fight to contain The Pestilence.
In 14179, the Pestilence reached its peak. While the exact number is unknown, estimates place the number of probes in the MIlky Way alone to be over 10 sextillion.
The Fornax War had a galaxy wide impact, both good and bad. The Probes are still a major problem. quadrillions of them are in intergalactic space flying to various galaxies. Even one ending up in a galaxy could spell disaster.
Many businesses that dealt with the development and manufacturing of weapons showed an increase of business with orders coming in directly from the Confederacy. People who didn’t want to fight were able to be hired there for extra income. Destroyed planets aside, the economy did benefit by the end of the war.
Due to the extensive damages caused by the probes. Self-Replicating Von Neumann Probes capable of interstellar flight have been banned. Most probes capable of self replication are used for large construction projects.
This war caused the largest amount of space pollution of nay conflict in the Borealis Cluster, just barely beating out The War for All in terms of shear pollution. It is estimated that, if left alone, the probes would be able to consume the entire Local Group in just 10,000 years. A few large companies, that receive government grants, constantly hunt down the remaining probes and destroy them before they can cause more damage.