D7 class The D7 class battle cruiser was a 23rd century warship originally designed and used by the Klingon Imperial Fleet , before being shared with the Romulan military during the late - 2260s . History . The D7 class Klingon battle cruiser was used during the 2256 Federation - Klingon War , although some versions , such as those used as prison ships , had a different hull configuration to ones used in the following decade despite using the same designation . ( ) The D7 class served as the backbone of the fleet for several years during the 2260s . ( , " et al . " ) Among the mission profiles designated for this class was that of scout ship . ( ) By 2267 , they were prominently featured in the Klingon Imperial Fleet , where they posed a serious threat to the security of the Federation and Starfleet . ( ; ) The Romulan Star Empire later began using the same design by 2268 . ( ) The battle cruiser began to replace the D7 class during the 2270s . The D7 was finally " retired decades " prior to 2377 . ( ; ) Interest in these vessels by the Federation continued to appear well into the 2370s , as data on this class was commonly found within numerous Starfleet files . ( ; ) At least one D7 remained in service well into the late 2370s , when one was encountered by in the Delta Quadrant in 2377 . ( ) Technical data . Physical arrangement . The D7 class was almost predatory in its appearance , with a spread - wing primary hull , long neck and head - like command pod . The early Romulan variants had a large bird - of - prey design painted on the hull , identical to what was found on the Bird - of - Prey . ( ) Other Romulan D7s had red and yellow feather - like detailing painted on the upper wing and nacelle pylon . ( ) The bulk of the ships overall mass was incorporated in the aft section of the ship . The bridge was located on the bulbous head , which was separated from the aft section by a relatively thin neck that flared out into the wings . Jutting from below these wings were a pair of outboard warp nacelle s . The ship ' s impulse engine s were located on the caudal section of the ship . ( ) . Variants used as prison ships had significantly more bulk in the neck area , creating an overall triangular appearance , in addition to more plating and protrusions all around , as well as different impulse engine housings . ( : " Choose Your Pain " ) This design had evolved from a classic design lineage dating back well into the 22nd century with the early D5 class battle cruisers . ( ) In terms of dimensions , it was comparable in size to the Federation ' s starship . ( ) Tactical systems . During the mid - 23rd century , the D7 class posed a significant threat to the Federation with the classes impressive armament consisting of two nacelle - mounted disruptor cannon s , a forward - mounted phaser emitter , and a forward launcher capable of firing photon torpedo es , magnetic pulse s and disruptor blasts . ( ; ; ) In 2269 , the Klingons developed a prototype weapon , described as a projected stasis field , which was first encountered on the by the Federation . The field could be projected in up to three different directions at one time . The weapon , which was extremely powerful , was capable of completely paralyzing an enemy vessel , including all its vital systems . It was however equally crippling to the firing ship itself . Ultimately , it was determined by the Federation that this was so impractical in standard combat , that it posed no real threat . ( ) While the D7 cruiser was often viewed as a threat to a " Constitution " - starship , under certain circumstances , it was possible for a " Constitution " to destroy a single D7 with a barrage of phaser fire . Following such an instance at the outbreak of the Federation - Klingon War in 2267 , the USS " Enterprise " encountered a fleet of eight D7s , which was considered by Captain James T . Kirk to have superior odds . Despite these odds , Hikaru Sulu was confident the " Enterprise " could have defeated them . ( ) By the late 24th century , these vessels were considered rather antiquated , and were identified as being inferior in firepower to a Federation starship . ( ) Cloaking device . Like its predecessor , the Romulan Bird - of - Prey , the Romulan D7 was equipped with cloaking technology . Klingon ships were outfitted with cloaking devices as late as 2269 . One of the first Klingon vessels to acquire the new technology was the . ( ; ) Propulsion systems . Some Klingon ships in the 23rd century were equipped with an S - 2 graf unit , which was roughly equivalent to the warp drive s in the Federation ' s starship s . The warp drive of the D7 enables it to catch up with a ship traveling at the speed of warp 9 . ( ; ) In addition , the D7 impulse drive consisted of four - port engines , presumably giving the ship enhanced maneuverability at sublight speeds . ( ) Shields . D7s were equipped with standard shield s , with their number three and number four shields being specifically located amidships . ( ) Tractor beams . The D7 class vessels were capable of creating a tractor beam , strong enough to hold a 2250s Starfleet shuttlecraft . ( ) Other systems . Romulan D7s were outfitted with food synthesizer s . ( ) Interior design . Crew complement . The average crew complement of a Klingon D7 was comparable to a " Constitution " - class , and consisted of around 430 . ( ) Main bridge . Referred to by the Romulans as " Control Central " , the bridge was the nerve center of the D7 class . ( ) Conference room . The conference room was used as a meeting place for the ship ' s senior staff for mission briefings . It contained a triangular table embossed with the emblem of the Klingon Empire , with each side of the table having its own set of chairs . Surrounding the table are various computer consoles . ( ) Appendices . Background information . Name origins . The term " D7 " remained the speculated designation for the Klingon battle cruiser for many years , at the time simply referred to as the " Klingon Battle Cruiser " in production sources , with origins rooting to an incident Gene Roddenberry recalls in " The Making of Star Trek " , which is linked to how he likened the cast ' s relationship to that of a family : The designation was not actually referenced on screen until " Star Trek " s 30th anniversary , in the DS9 Season 5 episode " Trials and Tribble - ations " , and later in the VOY Season 7 episode " Prophecy " .