The Federation’s greatest rival over the last century, the Klingon Empire occupies a large volume of space in the Beta Quadrant. Klingon society is caste-based, dominated by the warriors of the Great Houses. Beneath them are the lesser Houses, then the common population, and a dozen or so subject races.
The Great Houses maintain their own armies and fleets: in times of war these make up the Deep Space Fleet, which along with the standing Internal Security Force, form the Imperial Klingon Expeditionary Forces (later renamed the Klingon Defense Force). The disparate nature of the fleets means that the Klingons operate a wide variety of vessel types, although there have been moves towards standardisation since the 2250s. IKEF vessels are generally divided into battlecruisers and “birds-of-prey” (raiders), although both terms encompass many classes and roles.
While the majority of Klingon crewmen encountered are House warriors, noted for their tempers and obsession with personal glory and honour, their ship crews also include technicians and non-combatant crew from lesser castes. Non-Klingons are never found on Klingon vessels.