Cervalis V was an M-class planet colonized by the Federation in the early 24th century, not far from the Cardassian Union. When the Federation-Cardassian Demilitarized Zone was established in 2370, the colonists refused to relocate, and the planet eventually became a headquarters for the Maquis.
In the Pendragon timeline, the planet was attacked by Klingon forces in 2374. Over 50,000 Maquis and civilians died in the massacre, though a few managed to escape on vessels such as the SS Artemis. (Star Trek: Pendragon: "L'Morte d'Maquis", "The Good Fight")