A virus caused killbot factories to start printing omnicidal killbots. Each country's military was getting owned by the killbots so Overwatch was formed by soldiers from every military and some randos to shut down the factories. They suceeded, then became the world police. Robots were made to live beneath the cities and subject to "Detroit:Become Human" level discrimination. 10 years later, Overwatch was disbanded after a group betrayed them and bad press. 10 years later, some of the members came back to reform Overwatch.