In the Advanced Generation timeline, humanity migrated into space enacted under the Earth Federation's Mars Colonization Plan (also known as "Mars Birthday") 35 years' prior to the adaption to the A.G. Calendar. 150 years before the beginning of the series, people moved to the sixteen experimental colonies that were constructed in the Mars sphere. While Mars was initially thought to be a resource-rich frontier with sufficient space to address humanity's overpopulation, the colonization project failed when a botched terra-forming produced harmful particles from the surface which eventually lead to the fatal disease known as "Mars rays". The disease killed 20% of the settlers, and was named as such as the harmful particles can interact with the plasma in solar wind and produce aurora-like effects. The settlers were unable to prevent the spread of disease. With the botched investigations that followed, the migration plan was deemed a failure by the Federation government and was subsequently covered-up with the official report stating that there were no survivors.

The struggling population that remained in the Mars sphere founded a new nation led by Fezarl Ezelcant, with the desire to return to the Earth sphere. The new nation was called Vagan, and would be recognized as the Unknown Enemy by Federation forces. In hopes of finding a safe refuge on Earth, they instigated the One Hundred Years War by attacking the space Colony Angel in A.G. 101.