The Perry Line was a military designation for a group of eight planetary systems that marked the borderlands between Xi'an and Human-controlled space during the Xi'an-Human Cold War. Named after Armistead Perry, the Navy general who introduced the strategy in SEY 2542, the United Planets of Earth (UPE) designated the systems as no-fly zones and utilized them as military staging grounds. Each system was named after a god of war.
After the signing of the Perry Line Pact dissolved the militarized zone in 2793, the systems were divided evenly between the Xi'an Empire (SaoXy'an) and United Empire of Earth (UEE) governments. While the UEE maintained the original names for its systems (Gurzil, Horus, Oya, and Tohil), the Xi'an renamed the Hadur (Yā'mon), Indra (Kyuk'ya), Pallas (Th.us'ūng), and Virtus (La'uo) systems.