Humanity discovered Equestria and invaded it for resources, cheap labor force and lots of free land. Because of their vast military prowess and a significant gap in technology they did it virtually effortlessly.

Princesses are dead, other leaders are either captured or tortured. Only a small squad of ponies still resists, while the others are forced to live in reservations or transferred to Earth as slaves.

Humans are already celebrating a victory when ponies recieve aid that they least expected.