During the First Cylon War, Galactica along with the Columbia and one other unnamed Battlestar tooks part in Operation Raptor Talon; where the Columbia is destroyed with all hands lost.
Over 40 years after the war, Galactica, as one of the oldest ships in the fleet, was scheduled to be decommissioned and turned into a museum. Various conversions, including the Command Navigation Program (CNP) were scheduled to take place and most of her onboard squadrons were removed.
During the decommissioning ceremony, the cylon attacks on the colonies began. After a battle, including many direct strikes, Galactica successfully jumped away to the Ragnar Anchorage depot.
Galactica then leads and defends a small fleet of civilian ships on the search for resources and a new place to settle.