The warbird design referred to as D'deridex-class, B-type warbird, or Warbird class was one of the largest and most powerful mainstays of the Romulan Star Empire. It served as the backbone of the Romulan fleet during the latter half of the 24th century.
The uncloaking of a warbird of this type in 2364, during an encounter with the USS Enterprise-D on the edge of the Neutral Zone, signaled the end to fifty-three years of Romulan isolation. (TNG: "The Neutral Zone") Over the next ten years, these warbirds, under the command of both the Romulan military and the Tal Shiar, participated in numerous encounters with Starfleet and the Dominion.
By 2374, they were prominently featured in the Dominion War, where they were instrumental in forcing the Dominion fleets back, time and again. The design saw action during the First and Second Battles of Chin'toka, as well as the final showdown of the conflict, the Battle of Cardassia. (DS9: "Tears of the Prophets", "The Changing Face of Evil")
At least four warbirds were used in the Battle of the Omarion Nebula, joined with at least twelve Cardassian Template:ShipClass cruisers in a combined fleet of twenty ships. The entire fleet was ambushed and destroyed by a fleet of 150 Dominion ships. (DS9: "The Die is Cast") At least seven warbirds were present in the Federation Alliance fleet at the Battle of Cardassia. One is known to have been destroyed and at least five survived. (DS9: "What You Leave Behind")
The D'deridex-class warbird was classified as a battle cruiser by Starfleet. Using a forced quantum singularity as a power source and the latest in Romulan cloaking technology, the D'deridex was not only one of the most advanced vessels in the Romulan Star Empire, but also in the Alpha Quadrant. These warbirds were roughly twice as long as a Federation Template:ShipClass starship with a lower overall maximum speed. (TNG: "The Neutral Zone", "Tin Man")
The outboard plan of the warbird's design incorporated a unique, horizontally split "shell" hull design, with a prominent forward section. The bulk of the ship's overall size was incorporated in the open-shell, which resembled two separate "wings" that met at either side at the warp nacelles, at the "tail" and off the "neck", which was connected to the "head" or primary forward hull section. The "head" featured the bridge, main engineering, and a majority of the primary weapon systems of the vessel. (TNG: "The Neutral Zone", etc.)
The primary directed energy weapons array of a warbird was located in its "head", and consisted of a disruptor array, capable of firing both beams and pulses, which also appears to have been shared with a torpedo launcher. (DS9: "The Die is Cast"; TNG: "The Defector", "Face of the Enemy", "Timescape"; VOY: "Message in a Bottle") Some warbirds were also known to have been equipped with phasers. (TNG: "Contagion")
Three additional weapon arrays were located, one each, along the top of the upper "neck" support, along the bottom of the lower "neck" support, and at the tip of the "nose". (TNG: "Contagion", "Unification II"; DS9: "What You Leave Behind")
Like earlier Romulan ships, D'deridex-class warbirds were equipped with cloaking devices, which protected them from detection in most evasive situations. Like all cloaking devices, the D'deridex-class could utilize them when in defensive or combat situations. However, cloaked warbirds radiated a slight subspace variance at warp speeds; therefore, ships traveling at speeds above warp 6 ran a much greater risk of being detected through their cloak. (DS9: "The Search, Part I", "The Die is Cast") There were other unconventional means to penetrate the warbird's cloak. While traveling under cloak, all electromagnetic emissions, including communications, aboard a warbird were carefully monitored. (TNG: "Face of the Enemy")
The fact that a typical D'deridex-class warbird used a forced quantum singularity as its power source gave the ship type some vulnerabilities. If that system was not functioning perfectly or was damaged even slightly, it might have shown through the cloak as a magnetic disturbance of some kind. The destruction of the engine core of a D'deridex-class warbird usually led to the complete destruction of the entire ship.
In order for a warbird to remain undetected while under cloak, the radiative emissions from the warp engines had to be precisely balanced. A slight misalignment in any of the warbird's nullifier cores would create a small magnetic disturbance in space whenever the ship was in motion. This could make the ship detectable while cloaked. The effect of this disturbance, when it occurred, appeared intermittently as a polarized magnetic distortion. (TNG: "Face of the Enemy")
The use of the confined singularity limited the warbird's overall maximum speed. For a warbird to match the maximum speed of a Galaxy-class starship, it needed to exceed its engine output by thirty percent. Doing this would typically cause the warbird's warp drive to sustain irreparable damage. (TNG: "Tin Man")
The confined singularity could occasionally cause time shifts into the future. This occurred to Miles O'Brien for a brief period. As a result of this effect, he was able to prevent an attack on Deep Space 9 by a Romulan warbird. Also, if the singularity signature was carefully scanned, it could be monitored through the cloak. (DS9: "Visionary")
The primary color scheme aboard warbirds was distinctively beige and green-gray or teal.
Located in the front of the bridge, against the forward bulkhead, was the ship's main viewscreen. Directly behind this, and to the left, was the location of the pilot's console, which contained helm (and possibly navigator) functions. In some ships, the pilot stood at his console; in others, the pilot was allowed a chair.
The command chair was located near the rear of the bridge, on a raised platform. Around the perimeter of the command chair were various stations. (TNG: "Contagion", "Face of the Enemy"; DS9: "The Die is Cast")
Adjacent to the bridge was the commander's ready room or command center. Although appearing to vary by ship, one style included (but was not limited to) a large desk and couch, with removable table and a window that provided a view of outside the ship, such as showing a perspective of space when the vessel was in its normal environment. (DS9: "Improbable Cause", "The Die is Cast")
In some cases, ready rooms functioned as command centers, and included monitors and display consoles. This allowed the commander to monitor the control of ship or fleet activities without actually being on the bridge. (TNG: "Redemption II")
The wardroom was the conference or officers' room connected to the main bridge by a set of doors. Its function was similar to that of an observation lounge, but also served as the dining area for the ship's senior officers. (TNG: "Face of the Enemy")
The engine room section was located at the ventral base of the forward "head" of the warbird. Its layout was similar to that of a Galaxy-class starship, with primary situation station in the center of the room and associated consoles along the walls surrounding the room.
One outstanding difference between the main engineering of a warbird and other Romulan starships, likewise distinguishing it from those of the Federation and Klingon Empire, was the absence of a large matter-antimatter reactor core. In place of this bulky component, the Romulans had a wall compartment, which contained the quantum singularity engine core. (TNG: "Timescape")
The crew quarters aboard a warbird were located on the ship's "C" Deck. They were sparsely furnished, with a table and chairs in the center of the floor, and a set of bunk beds incorporated into the walls. Crew quarters could also have force fields integrated in and around their bulkheads. (DS9: "The Die is Cast")
- IRW Belak
- IRW Decius (illusory)
- IRW Devoras
- IRW D'ridthau
- IRW Haakona
- IRW Khazara
- IRW Makar
- IRW T'Met
- IRW Terix
- "The Neutral Zone"
- "Where Silence Has Lease" (illusory)
- "The Schizoid Man"
- "Peak Performance" (illusory)
- "The Enemy"
- "The Defector"
- "Tin Man"
- "Future Imperfect" (illusory)
- "Data's Day"
- "The Mind's Eye"
- "Redemption II"
- "Unification II"
- "Face of the Enemy"
- "Birthright, Part II"
- "The Pegasus"
- ENT: "Future Tense" (database image)
The designation of "D'deridex-class" was first mentioned in "Tin Man", the designation as "B-type" is mentioned in "The Defector", which could be seen as an aptly conceived designation since it coincided with the introduction of the slightly differing second studio model (see below). The ship is also referred to as a "warbird class starship" by Picard in "The Defector".
The warbird that appears in "Contagion" is referred to as a "battle cruiser", which seems to be an inaccurate classification for a vessel of this size. However, according to the script for that episode, the Romulan vessel was also referred to as a Bird-of-Prey.  This indicates that the warbird model may not have been intended to be used in this case, and that the battle cruiser reference was never changed to reflect the model used. It is also possible that the Romulan battle cruiser mentioned in TNG: "Angel One" may too have been the yet-unseen D'deridex.
On the occasion of the episode TNG: "The Neutral Zone", the producers were mindful that the re-introduction of the Romulans in the franchise needed to be memorable, with a likewise memorable ship, in the script simply referred to as "Romulan cruiser", to go with it.
The D'deridex-class warbird was the last new ship designed by Andrew Probert for the show, his design sketch of 21 March 1988 receiving the approval of the producers. (The Art of Star Trek, p. 83) On his design, Probert later remarked:
"The Romulan Warbird from the original series had, of course, a bird design on it. And I wanted to stay with that in someway. So, I started with bird and bird wing shapes. And eventually came to a design similar to what is on the screen. But my concept was to have one engine above and one below, because I felt that having a vertical design alien ship in front of the Enterprise, which has a very horizontal configuration, would be a nice contrast of ships.
"Now, Gene dictated that there are no three-engine starships and no single-engine starships [....] And then I started thinking that, back in World War II, all the nations that had fighter aircraft and airplanes did the same thing: they took off, they flew, they landed, they maneuvered. They usually had one engine, two wings, two tailwings – so they all had the same components, but they all looked different. There was a national design bias to each aircraft, but technically they all did the same thing.
"So my thinking was in Star Trek – since the Enterprise used to have two engines – I came up with the idea that the engines had to reach out to each other in order to work co-dependently. In other words, there would be no obstructions between the engines to disrupt the energy fields or connecting forces between them. And, well, all the alien ships could look different but still operate in the same principle. So that's why [...] [for] the Romulan Warbird, the engines would see each other through the ship. The ship is built above and below the energy field of those engines.
"But my original concept would be that there was a lot more ship, a lot more structure, packed inside those wings. So it was, looking like two big wing sections, obviously big enough to contain people and cargo. But my original concept had them bigger." wbm
Experimenting with the vertical design concept, Probert further elaborated on his design process, "I didn't have any information except that the Romulans were coming back and that we had never seen their ship before [In TNG]. Since the Enterprise is so horizontal, I wanted to contrast it with a vertical ship. At this point we didn't see Gene Roddenberry anymore. Gene had always been open to suggestions. I was in awe of how he had created the show, and my respect for him was enhanced by the fact that he would sit and listen to your ideas. He may not have always used them, but he would always listen. I felt that if I had shown him the vertical warbird and explained my reasoning, he would have considered it. But that didn't happen." However, Probert was was told by another producer, "Let's make it horizontal instead". "So I created new preliminary drawings, and being that it was a war bird, I continued the birdlike motif from my earlier sketches." Conceding to the request, Probert also proceeded to add a bottom wing to his now horizontal design. Continuing, he further clarified, "I hadn't thought about putting a bottom wing on there, but I looked sideways at one of my earlier vertical drawings and thought I'd add a loop to see how that worked. I drew that final image as a scale reference to the Enterprise, just to show the difference in size. I love even numbers, so the warbird is 4,440 feet long. The thing is, I provided this image to the producers purposely to suggest that the scene be filmed with the Enterprise in front, obviously closer to us, yet the warbird is still larger. Unfortunately the visual effects people reversed the shot and you really had no idea how much larger the Romulan ship was." (Star Trek: The Next Generation 365, p. 132)
Physical studio models
The original studio model was made of cast resin and acrylic plastic. Built by Greg Jein in the month following its design approval, it measured 36" × 25" × 10", debuted in TNG: "The Neutral Zone" and was last seen as stock footage in DS9: "By Inferno's Light". Jein noted on the build, "I enjoyed working on the Romulan ship, because it was such an unusual shape. We did that pretty fast. Again, we, because it was such an unusual shape, we had to carve that out of flores foam and we vacuformed on top of that and we take the foam out, so we had a hard shell, so we could put the armatures and lights in." (TNG Season 4 DVD special feature "Select Historical Data")
The appearance of the D'deridex-class model has caused some confusion in regards to the color scheme. Well-known early publicity stills, especially in the 1980s Starlog Press publications, showed the model both in a green-gray color scheme and a metallic blue-gray color scheme (mostly to represent ships of the Tal Shiar, notably in DS9: "The Die is Cast"). This was partly due, in the case of the first one, to "tweaking" the colors in post-production.
However, the other explanation for this was that the studio had two models made, the green one and best known being the original, first one, and that they used them both.  Co-built, again at Jein's modelshop, by model maker Bruce MacRae, and almost identical to the original studio model, the second, blue-gray model differed from the green one in that, apart from the color, it had an additional feature added on the outer sides of the warp engines and it debuted in TNG: "The Defector". It is not clear why the second model was commissioned, though Daren Dochterman has given a possible explanation; "On other occasions, it's done to give an in-house model crew something to do to justify billing the production company for it... and to maintain its existence." 
It was the second, blue-gray model, that was included, as Lot #702 , in the 40 Years of Star Trek: The Collection auction, estimated at US$8,000 to US$12,000, where it was sold at auction on 7 October 2006 for a winning bid of US$30,000 (US$36,000 including buyer's premium). It was sold to British collector Adrian Hancock, who had also managed to acquire the USS Voyager and USS Enterprise-C studio models in the action.  In a run up to the auction, making its only public appearance, the model was on tour at the Creation Convention in Las Vegas from 17 August to 20 August 2006. 
Other physical models
In the episode TNG: "Future Imperfect", a display model can be seen aboard the Romulan Warbird IRW Decius. The model was an otherwise unmodified piece from the AMT/Ertl modelkit No. 6858. This constituted the only time an alternative model was used to physically represent the class in any of the live action productions.
A limited production run of twelve, built from the same molds as the original studio model, was later sold in 1997, with a certificate of authenticity signed by Greg Jein at the Viacom Entertainment Store in Chicago, sporting yet another slightly differing color scheme, gun metal blue-gray, and without the extra detail on the warp engine assembly. wbm
For the later seasons of Deep Space 9 and Voyager, a CGI model was built at Foundation Imaging, making its debut in VOY: "Message in a Bottle". The first, green-gray model was used as reference, so the variant with the additional detail on the warp engine assembly was initially no longer seen from then on. That was until DS9: "The Changing Face of Evil", when a close-up of a severely damaged warbird was needed. Foundation's model was modified at Digital Muse to showcase the damage and the modeler at Muse made use of the opportunity to add the extra nacelle detail and color-correct the model to resemble the second physical studio model.
The studio model of the Mazarite warship, from ENT: "Fallen Hero", was kitbashed from a D'deridex-class AMT/Ertl model kit, No. 6858, by Dan Curry, using the upper wing structure to be "sold" to the producers. The producers "bought" the design, and the prototype model was subsequently recreated in CGI at Foundation Imaging by Koji Kuramura and mapped and animated by Robert Bonchune.  This CG model was later reused as the Illyrian starship seen in ENT: "Damage". This was one of the very few times that a design feature of a signature "hero" ship was recycled to represent an alien design.
The following information of specifications and defenses comes exclusively from the Star Trek: Deep Space Nine Technical Manual:
- Production Base: Unknown; Romulan Star Empire
- Type: Heavy Cruiser
- Accommodation: 1,500 plus officers, crew, and troops
- Power Plant: One artificial singularity-drive warp core feeding two nacelles; two impulse system
- Dimensions: Length, 1,041.65 meters; beam, 772.43 meters; height, 285.47 meters
- Mass: 4,320,000 metric tonnes (est.)
- Performance: Warp 9.6 (observed)
- Armament: Six ship-mounted disruptors; two photon torpedo launchers
Some of this information contradicts data from the original specifications of warbird designer Andrew Probert and also some observations of the D'deridex-class in canon episodes.
- Star Trek: Starship Spotter. Adam "Mojo" Lebowitz & Robert Bonchune. New York: Pocket Books, 2001. ISBN 074343725X
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