Trekipedia

Cheron

Site of a battle with the United Federation of Planets in the Omicron Gruis System,^[3] which was considered a “humiliating” defeat by the Romulans, according to Admiral Jarok. It led to the creation of the Neutral Zone and thus likely the climax of the Romulan War in 2161.^[2] By coincidence, it was also the name of a long-dead world where a group of two advanced races destroyed each other over racial bigotry, not encountered by the UFP until 2268.^[1]