This article contains canon information but has fanon info added to it. Therefore, this article shouldn't be deleted, since this article also contains fanon info. The canon version of this page can be viewed here.
On Sentai Mountain, there was a peaceful civilization where advanced Robots and the ancient way of life went hand in hand. But one day, a golden robot named Meca One led the robots to revolt against the Humans. Fights between the humans and robots broke out, unleashing uncontrollable energies that divided the mountain in two. The humans eventually overcame the robots, and cast them into the gorge.
The humans built bridges to link the two halves of the mountain. Some humans, including Sensei Keiken, feared that the robots might come back someday so Sensei Keiken promptly began to construct armored battle machines for defense. But before the humans' preparations were complete, the robot legions, armed with battle machines of their own, caught the humans by surprise and quickly seized control the southern half of the mountain. More powerful than ever, their primary aim was this: to completely drive humanity from Sentai Mountain. Sensei Keiken hurriedly recruited new pilots to man the battle machines and Exo-Force was born.