>u>Battlestar Group 75 (a.k.a. 75th Battlestar Group) is the Colonial Fleet unit that battlestar Galactica was assigned to at the time of the Cylon attack. It is often abbreviated (including on the Galactica's crest) as "BSG 75."
Battlestar Group is seen by RDM as analagous to a modern-day Carrier Battle Group, comprising at least one battlestar, plus a number of support vessels. Given the number of available battlestars at the outbreak of hostilities with the Cylon attack, it is possible that a battlestar group may have comprised a number (3-4) battlestars operating as a single unit, supported by additional Colonial vessels.
Given that battlestars were doubtless reassigned to different units during and after the Cylon War, it is likely that the 75th Battlestar Group was one of the final (and perhaps oldest) groups to be in the service of the Colonial Fleet prior to the Fall of the Twelve Colonies.