The Striker was a Colonial vessel which escaped the Fall of the Twelve Colonies and joined with the Fleet. It remained loyal to Commander William Adama during the short-lived schism between the military and civillian governments following the attempt on Adama's life by Cylon infiltrator Sharon "Boomer" Valerii (Kobol's Last Gleaming, Part II).
The Striker was damaged in a collision with a fuel tanker during this time due to the incompetent oversight of recently promoted Captain George Birch, CAG for Galactica in Lee Adama's absence (Home, Part I).