In the 24th century AD, the solar system has become the dazzling stage of human civilization, with countless colonies multiplying among the planets and asteroid belts. However, behind this abundance are increasingly tense competition for resources and geopolitical conflicts. The rift between the "United Front" led by Earth and the "Independent Alliance" led by Mars is growing day by day. In order to compete for the control of rare minerals in the asteroid belt and colonies in the outer solar system, the two sides built steel defense lines called "orbital fortresses" at key orbital points.
