In late 2375, the Breen became allies of the Dominion, where they committed a large fleet of ships to join the war effort. Worf and Ezri Dax were brought aboard a ship after being captured by the Breen on a planet in the Goralis system. (DS9: "Penumbra", "'Til Death Do Us Part")
The Federation first encountered the ships in combat during the Second Battle of Chin'toka. The Cardassian and Dominion ships held back while the Breen engaged the Federation, Klingon and Romulan forces. The ships had been equipped with energy dissipators that disabled the Allied ships' engines, weapons, and shields. The weapon was instrumental in defeating the Allied fleet and forcing the Federation Alliance from the Chin'toka system, losing the only enemy territory that they held in Cardassian space. (DS9: "The Changing Face of Evil") Fortunately, the Klingon Bird-of-Prey IKS Ki'tang was not affected, leading to a defense being discovered. (DS9: "When It Rains...")
Even without the energy dampening weapon, the Breen ships proved to be formidable. One such ship destroyed Legate Damar's ship in orbit of Cardassia Prime. Several ships participated in the Battle of Cardassia. During this engagement, a Breen ship was able to outmaneuver the USS Defiant, displaying exemplary maneuverability. Besides the energy dissipator, Breen ships mainly attack with torpedo weapons fired from at least three forward launchers at the pikes of the ship. Several Breen ships were destroyed by the Cardassian fleet when the Cardassians joined the Allies. Breen ships were also deployed in orbit of Cardassia Prime after the Dominion's retreat. (DS9: "The Changing Face of Evil", "The Dogs of War", "What You Leave Behind")
Ships of the class
- "Designing the Breen ship", Ben Robinson, Star Trek: The Magazine Volume 1, Issue 7, pp. 48-52, November 1999
- Star Trek: The Official Starships Collection, issue 69, March 2016
Breen warships appear in Star Trek Online as a part of the game's "Season Two" update. They are referred to as the Chel Grett class, a name that also appears in the Fires of Armageddon sourcebook. A playable version of this vessel was released as part of the 2012 winter event. For the 2016 one, an upgraded version named Chel Boalg was made.