2055-2390: Canonical Killzone Events (Read the Killzone timeline page on the Killzone wikia to learn more about the events of those years)
2391: The third extrasolar war erupt between the Vektan and Helghans communities on the planet Vekta. VSA forces quickly overwhelm New Helghan forces thanks to new military technologies provided by the UCN. New Helghan is occupied by the VSA and every Helghan military technologies and facilities are taken over. The ruined planet of Helghan is re-colonized by the UCN due to its immense amount of Petrusite which could be used for the mass production of extremely powerful weaponries and others types of technologies. Most of the Black Hands operators are captured and publicly executed by the VSA troopers. The Helghan government is no more, instead being completely absorbed into the UCN.
2392: Due to an ever growing sense of paranoia, the UCN become an almost-fascist like government and strengthen its ties on all of it's colonies. The United Colonial Army get funded extremely high amount of credits to undertake major enhancements as a way to prepare incase of another colonial rebellion. Meanwhile, the hostility between humans and helghans slowly fade off as the laters ones are introduced to human civilization again, the helghans people's being granted life on the vektan side of the wall. The Helghan side of the wall become a massive military complex for the UCN. The UCN undertake a massive operation to make the planet Helghan to be inhabitable again.
2400: Helghan is now inhabitable once again. The planet is full of Petrusite mines, research facilities, training camps, military facilities and etc. Despite being free of the petrusite fields that once polluted the whole planet, it is still as harsh as before the Terracide and the humans personnels living on the planet are issued advanced HAZMAT suits and gas masks and are mostly secluded into large, sterile bunkers and buildings with artificial oxygen. Several technological discoveries boost up the military might of the UCN this year. Infantry-sized laser weaponries are now commonly used by the UCN and prototypes Petrusite rifles are also produced, designed to be more powerful than the previous Stahl Arms petrusite weaponries.
2412: Helghan people's slowly "mutate" back into humans beings as they now mostly live on the Vektan side of the wall. The UCN now count more than 1300 colonies, around 500 of which are extremely well developed and well defended. Every major UCN colonies have large amounts of UCA garrisons and fleets orbiting those said planets. The ISA still maintain an important role in the defense of the lesser developed planets. Human space has been in relative peace for several years as of this year.
2413: Cell regeneration technology is mastered by humanity, granting an average human being (Including Helghans) an average lifespan of at least 500 years without physically aging. (Alright, honestly thats just a plot twist so original killzone characters can still live and so can the Helghasts after so much years. But yeah, incase we mastered cell regeneration, I'm pretty sure we could extend our lifespans, perhaps not as much but at least by a couple hundred years)
2500: Helghans are now once again humans, but still conserve some helghans characteristics such as an increased musculature, physical force and resistance to harsh environment. Humanity perfect the FTL warp technology, now being able to go over 100 Light Years/Days.
2600: Fusion technology is perfected, the UCN and it's ISA commands now being able to develop extremely powerful infantry-sized directed energy weapons such as laser and plasma blasters.
2700: Due to the Cell regeneration technology, the helghast "specie" still exist as it was, however the descendants of those helghasts slowly became humans back. Humanity, especially the UCN, now have an extremely powerful military might as well as an total population exceeding the 2 and a half trillions humans, spread through the 15 thousands UCN colonies. Humanity discover ways to synthetise the Petrusite artificially. Energy shielding technology is perfected, extremely resistant metallic alloys are also synthesized and UCN vessels are retrofitted with newer technologies. ISA commands are established in most of the colonies solar systems. Even the weakest ISA commands established on the newest colonies are considered forces not to be challenged with. An alien structure is discovered on Mars. Due to this discovery, humanity becomes extremely paranoid, fearing an alien invasion even if the alien structure is several thousands years old. This collective fear of Alien invasion unite humans colonies more than ever. Element Zero technology is discovered and exploited to perfect Humans techs but is not extensively used for weaponries as directed energetic weapons are considered more powerful than the mass accelerated slugs throwers that could be produced with Element Zero. The Charon relay is discovered and quarantined by the Earth Second Defense Fleet of the UCN. The colony of Shanxi is founded and Relay 314 is also discovered but the ISA garrison on Shanxi is relatively weak due to this colony being the newest and least developed one despite housing more than 9 millions colonists.
October, 3, 2600: The relay is activated from the other side.