Rise of the Hunters

The Hunters were used to suppress and eliminate citizens of their own nations and within friendly territory. This led the AI to determine that there is no such thing as friend or foe as long as they are controlled, and that any human could become a threat, therefore they are all threats. Thus began the war to end all wars.... and it would stretch humanities survival to its limit.
Human civilization was on the brink of total collapse. Fighting off the Hunters with traditional weapons was a losing battle, and after ten long years of horror, two impossible decisions were made by the remaining authorities - use what few resources they had left to seek the safety of subsurface shelters, and do whatever is necessary to ensure the survival of the species, even if that meant destroying the outside world. A mad dash to makeshift safe zones caused widespread panic, creating even more chaos for military personnel trying to help save lives. Ultimately, a small percentage of refugees were able to make it to various camps and the rest were left to fend for themselves.
Massive underground bunkers called Arks were established to ensure the survival of the species. Densely populated areas were far too dangerous, so four remote locations were chosen for the Arks - the tundra of Siberia, the Australian outback, the Andes mountains, and within the Grand Canyon in North America. Each subterranean complex was to be governed by their local military. Outfitted with weapons, rations, resources to sustain approximately 25,000 people, construction equipment to expand and maintain the space, and everything else needed to support subsurface existence. Less than one tenth of one percent of the Earth’s population were able to make it into these sanctuaries, and while they were the lucky ones, they also had to face the reality of living underground for an indefinite period of time. Communications into and outside of the Arks would be nearly impossible once comm network infrastructure was destroyed. Each community was truly on their own.
On a cold evening in 2135, the sun set on humanity’s world for the last time. The launch of nuclear warheads was initiated around the globe in an attempt to destroy the mechanical monsters, targeting major population centers where the most Hunters would be gathered. While the last humans on Earth hid deep underground beneath the safety of the very thing they were destroying. The greatest fallout from this war wasn’t the human population and all its achievements, but the Earth itself. Humanity's greatest structures were decimated and the atmosphere compromised, allowing the sun’s rays to scorch and irradiate the surface as it hasn’t for billions of years. Lush forests were turned to ash, cities burned, and a vast apocalyptic wasteland remained of the once blue planet. This was The Fall.
But the human spirit lived on. What remained of society came together to rebuild. Humanity may have been forced underground to survive, but that did not stop its greatest scientists and engineers from one day returning to the surface.
One hundred years after the fallout from nuclear winter had taken effect and dissipated, decades of planning and preparation would come to fruition. Under extreme precautions, seals on the bunker were opened and construction began on what would become Bastion, the last city on Earth.