This is the plot for the flash game Not Your War.
Rhea was one of the colonies of the Human Empire. Such colonies were created by sending unmanned ships decades before colonization, to prepare the climate and surface of the planet for the colonists. These unmanned ships used A.I. driven self-improving bio-mechs, called the Creators, to prepare the proper devices used for the climate change. Usually, when the colonists arrived on such planets, there was only ruins and scrap metal left after the Creators. But Rhea turned out to be different. It was so resourceful, gushing with water and filled with precious minerals, that the Creators had reached they full potential. Not only did they turn the planet into a perfect habitat, but also they perfected each other so much, that consciousness was born in their artificial brains, a phenomenon carefully avoided within the Empire. They multiplied and inhabited the planet, and send a message home, that claimed that Rhea was rightfully theirs.
Meanwhile, the Empire was dying due to lack of resources, that turned out to be essential in the process of prolonging the human life. Immortality, that has been achieved hundreds of years ago, took its toll on the human economy. All the Empire residents, that become accustomed to eternal life, now slowly begun to feel the bight of death, creeping on them once again. As soon as dying started to decrease their ranks, a decision was made to get the resources that Rhea possessed, using the most peaceful methods as possible. A colonization ship was sent, along with a strong military force.
The Creators agreed to all terms of the proposed resources exchange, which turned out to be a bluff. They correctly predicted that mortality will force the Empire to acquire resources of Rhea no matter the cost, so the moment the imperial fleet reached the atmosphere they launched a full blown attack. Despite the losses taken on the first day, the fleet managed to break the defenses, deploy ground forces, and then progress slowly taking control of the planet. What was meant to be a one-time battle, as the Creators hoped, turned into a war that destroyed the surface of the planet, changing Rhea into a sea of ruins and bare land, and lasted for over two years. As the resistance of the Creators was finally being broken, during an air battle, a young general by the name of Ian Morgan, one of four generals of the Imperial army, was shot down. While on the ground, he helped one of the Creators, a female fighter called Asha. While talking to her, he discovered how intricate and valuable were the Creators, and how wrong was destroying them, even when preserving them meant that humanity would become mortal again.
After returning to his men, general Morgan withdrew the whole division from the fight. As punishment he was stripped from his rank, and ordered to board his ship and return to the Empire for processing. He did not comply, instead he teamed up with the remaining Creators and begun his fight with his former allies.
Dominance War IV Champions are here!