Sub Region was similar to the vassal, the approach that System provided for a faction to annex another faction without needing war declaration. Of course, the annexed faction remained as a faction, but instead of an independent faction, the annexed faction would be recognized as a sub region of the faction that annexed them. Similar to vassals, the annexing faction had full control of the Sub Region.
The Sub Region was unlocked at the level 7 smart base, so the System officially recognized the association instead of relying on the System Contract. There was also an alliance approach where the faction in equal standing formed an alliance, just like what the World Government did, but officially recognized by the System. There were so many things unlocked after Zhang Mengyao upgraded the smart base to level 10.
