In 2055, an oil shortage triggered a global meltdown that resulted in a world war. When the dust cleared, and with Earth depleted of natural resources, it became apparent that if humanity were to survive, new worlds would have to be colonized. A coalition of Earth's wealthiest nations and companies was formed, termed the United Colonial Nations. Through colonization of the Terran Solar System (including Earth's moon), and star systems beyond such as Alpha Centauri, human life on Earth was able to endure and eventually thrive.The Current population of Earth is about 25 Billion people 
As of the Second Extrasolar War, Earth remains the capital world of the UCN. During the conflict it was the target of an intended petrusite bombardment by the Helghast, but ISA forces were able to foil the attack before it could be launched.
- ↑ 2013-02-28, The Killzone Universe: Complete Timeline & Backstory. NeoGaf, accessed on 2013-05-17
- ↑ Killzone 3