The Eurondans had co-existed for centuries with an enemy that grew to control most of the land mass of the planet. They referred to their enemy as "Breeders" because they reproduce with no regard for genetic purity. Civil war began when the Eurondans built an underground facility and used gas pipes from underground tanks to poison the planet's surface and exterminate the Breeders. SG-1 refused to support the racist policies of the Eurondans, and as the planet's surface became increasingly unlivable, Eurondan defenses began to fall to the Breeders.
Cross Reference: Aero-Fighter Weapons System, Alar, Beta-Cantin, Euronda, Eurondans, Farrell
Episode Reference: The Other Side