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 later 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")
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 Keldon-class 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 (see Black hole starship) 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 Galaxy-class 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.) Andrew Probert, who designed the D'deridex-class warbird, intended for it to have a length of 4,440 feet (1,353 meters).  He writes, "The wings were to have had a LOT more substance to them (as seen in my drawing) but was reduced [on] the model. They are separated to allow the engines to 'see' each other and generate a warp field. As previously noted on the board, I did not design the subsequent ships that ignore my attempt at requirements-for-warp-drive continuity." 
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")
Firing forward disruptor beamsFiring forward disruptor pulsesFiring forward torpedoesFiring phasers
(inner upper array)Firing disruptors
(outer upper array)Firing disruptors
(nose array) Add an image to this galleryAlthough not mentioned on screen, the original Andrew Probert design of the warbird was to have a single torpedo launcher positioned at the upper "nape" of the ship, at the top foremost position of the upper "shell". In addition, the warbird was to have a total of ten disruptor emitters, positioned in various locations on the model. These positions included: one pair on the "head" (one on either "cheek"), one pair on the vertical structure at the aft end of the ship (one on either side), two pairs on the aft edges of the port and starboard dorsal and ventral wings (one emitter at each location, for a total of four), and one pair at the dorsal apex of the ship. However, two other emitters are seen on at least one warbird, namely in the "nose" (pictured) and top part of the upper "back" (shown in TNG: "Contagion"). 
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. As was the case with virtually all cloaking devices, the warbird could not have its shields and cloak active simultaneously. 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. One of the most effective methods of doing so, pioneered by the Dominion, was to use an anti-proton beam scan, which proved to be effective in almost every situation in which it was used. 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 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 top speed of a Galaxy-class starship, it needed to exceed its maximum 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 potentially cause time shifts into the future. This occurred to Starfleet Chief Engineer 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") Regarding the impulse engine, Andrew Probert writes, "[It was] omitted by a tight schedule [...] but it would have been recessed into a vertical slot starting just below that landing bay and ending symmetrically below. The reason there are few (if any) side windows at the back area of the ship is because that's where that engine & power plant would have been." 
The warbird was equipped with at least one tractor beam, located in the forward section of the warbird, specifically in the lower "neck". (TNG: "The Mind's Eye") Although several features of the warbird were never addressed on screen, Andrew Probert has noted the locations of several unmentioned components, including the locations of the aforementioned weapon systems.'The navigational deflector is supposed to be a "V"-shaped faceplate located on the "face" of the ship. However, the center of this faceplate was instead featured as the primary disruptor array/torpedo launcher by the visual effects editors. Since Probert has identified at least one of their placements on the physical model, it is now possible to count at least twenty-six escape pod hatches on the warbird, thirteen on either side of the ship's dorsal spine. 
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")
Major variations in bridge design included a side-by-side seating arrangement for the commander and sub-commander. (TNG: "The Neutral Zone") Bridge of Tebok's warbird, 2364Bridge of the Haakona, 2365Bridge of the Khazara, 2369Bridge of Lovok's warbird, 2371 Add an image to this galleryAt least four different types of D'deridex-class bridges have appeared in Star Trek, each significantly different than the next. Although rather consistent in terms of layout, these variations – including positions and design of auxiliary consoles/stations, style of command chair and design of viewscreen – appear to vary as much between warbirds as they vary between different Klingon Birds-of-Prey.'The bridge that appears in "The Die is Cast" is, by far, the most elaborate, as the set was a reuse of the Constitution-class refit-bridge set originally constructed for Star Trek: Phase II.'The bridge in "Face of the Enemy", was also quite elaborate. According to the script for "Face of the Enemy", the original bridge layout placed the command chair to the far back of the bridge so that 'no officer went unsupervised'. This, however, was not how the final layout for the bridge was designed, as there were consoles positioned just outside the commander's peripheral vision, or even directly behind the commander's chair. The bridge that later appeared in "The Die is Cast" placed several auxiliary consoles well behind the commander's field of vision.'
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") This would seem to indicate that a meal preparation room was located near the ward room, in order to best facilitate the serving of the officers' prepared meals.
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") According to Andrew Probert, the engine room is "in the dorsal 'hump' just aft of the twin disrupter mount and you can see an indication of the energy conduit shielding running down to the warp engine in my [Ships of the Line 2010] calendar painting." 
A shuttlebay was located two decks down from the ship's "C" Deck, in Section 25. This area was large enough to contain at least one Starfleet Danube-class runabout. (DS9: "The Die is Cast") According to Andrew Probert: "Look on the plastic model and see the indented area on the top of the aft end... that is the landing bay door." 
The cargo bays served as storage areas for the ship's cargo, and possessed shelving space along the walls opposite of the main cargo bay doors. (TNG: "Face of the Enemy") According to Andrew Probert, the original design of the warbird was to have two large cargo bays centered on each side of the foremost position of the lower "shell". 
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") The crew quarters that appear in "The Die is Cast" were a redress of a set normally used for all crew quarters aboard the USS Defiant. Variations are known to have included a bed fully detached from the wall, and a sink with mirror along the far left wall from the entryway. (TNG: "Face of the Enemy")