Hive War

The Hive War took place twelve years before Broc left his house to escape the robot horde. It was caused by Doctor Yi and his team creating a mass mind for all the machines on the planet to collectively work together. After around two and a half weeks of machine and man living in harmony, the machines turned on the humans and began the long and bloody war, which destroyed most of the planet's surface. It ended after the hive mind was destroyed by a strike team from the collective nations of survivors. However, the scattered machines still could work together enough to create new machines. They dominate the surface of the earth to this day, yet unable to destroy the last few bastions of human civilization.