Earth Chain - Fierce Battle with the Saturnians

On the vast earth, humans have built huge alloy city walls, which can be seen from space. Not only are the city walls a chain of the earth, but the planets conquered by humans are also connected into a chain of the earth. The Earth Chain was born to defend against the barbaric and cruel Saturnians. Why did the Saturnians invade Earth? What is the purpose of the Saturnians invading the earth? Why risk everything? What conspiracy is this? Who won the final victory? Is it human? Or a Saturnian? It's all in the Earth Chain - a fierce battle with the Saturnians.