A variation of the B'rel Bird of Prey popular within the Klingon navy since the 2270s, the D-12 is a design plagued by problems. The designers attempted in the D-12 to refine the hull and increase the overall firepower of the ship. In this they managed to succeed. However, power problems plagued the D-12 Bird of Prey line. Weapon systems would not necessarily shutdown or fail due to these power spikes, but systems that were more sensitive tended to fail at inappropriate times. Faulty plasma coils in the cloaking devices onboard these ships were prone to a cascading shutdown because of the problem, and this eventually led to the class being phased out of active service. They were not mothballed, however; instead they were sold off to Klingon houses as honor guard and local defense craft.