Driven by a deep sense of duty and a love for his country, Damien abandons his burgeoning career as a doctor and joins his brother, Teddy in a dangerous and violent fight for freedom. As the Irish freedom fighters bold tactics bring the British to a breaking point, both sides finally agree to a treaty to end the bloodshed. But, despite the apparent victory, civil war erupts and families who fought side by side, find themselves pitted against one another,...

After 40 years absence, the Cylons return and launch a sneak attack on the colonies. The Battlestar Galactica and its fighter pilots can't prevent the colonies' obliteration. The Galactica leads survivors to find the 13th colony, a planet called Earth.

This season finds the twelve colonies caught in a brewing civil war between the followers of President Roslin and those of Commander Adama. They must face the Cylons from outside, and within, the fleet.