The World

The old world ended at precisely 11:22pm, on the fourth of December, 2033.
In the preceding decade, advances in human cloning had led to the development of the ultimate weapon - the expendable human clone soldier.
Mass produced in cloning factories, and armed with the type of organic intelligence that robots could never match, these clones replaced traditional soldiers at the frontline. Unlike previous conflicts, wars over dwindling resources could now be waged cheaply, and without the ethical constraint of the previous wars.
Nations begun aggressively expanding their borders, seeking more resources to create an ever bigger clone army. The entire planet soon became embroiled in an unprecedented world war.
Until 11:02pm, on the fourth of December, 2033.
In their final moments of desperation, besieged by millions upon millions of clone soldiers, one nuclear-armed superpower launched all of their nuclear arsenal. Before the last missile left its silo, the hair-trigger automated defense systems of every other nuclear superpower responded in kind. Millions of nuclear-tipped missiles flew past one another in mid-flight. Anti-missile defenses spewed forth, but no superpower had an adequate defense against everyone else. According to the survivors, the skies turned red as some of the missiles were intercepted...
... and at precisely 11:22pm, on the fourth of December, 2033 - the remaining missiles struck their targets.
With the mutual destruction of the old governments, the power they once held was now distributed amongst surviving military factions. Mostly made up of real human armies who had sought shelter in underground command posts, they soon aligned themselves with the major corporations that emerged from the ashes.
Equipped with only old world weaponry that survived in the underground bunkers, these armies for hire would soon become embroiled in the next big battle between the corporations - the race to rebuild the human clone soldier.