The ship's high cost, together with political factors, kept it from achieving widespread use in the Empire and units were assigned only to the most elite pilots. The starfighter played a major role in the Empire's campaign against rogue Grand Admiral Demetrius Zaarin and units participated in several other battles including the Battle of Endor. However, the advanced starfighter attracted the attention of several other factions and the Empire struggled to prevent the spread of the technology.
Following the death of Emperor Palpatine at Endor, the TIE Defender continued to see limited use by the Imperial Remenat up to at least 44ABY, and was involved in numerous conflicts, including the Yuuzhan Vong War.
The high success rate of more advanced Rebel starfighters against standard Imperial TIE Fighters resulted in a mounting cost of replacing destroyed fighters. That, combined with the realization that the inclusion of a hyperdrive would allow the fleet to be more flexible, caused the Imperial Navy to rethink its doctrine of using swarms of cheap craft instead of fewer high-quality ones. That led to the introduction of the TIE Advanced x1 and its successor, the TIE Avenger, and the TIE Defender itself was touted as the next "logical advance" of the TIE Series—a starfighter that was fast, well armed and capable of hyperspace travel.
Sienar Fleet Systems followed specific Imperial instruction in developing the TIE Defender, among them the requirement that the fighter would exceed the mission capability of a flight group of four standard TIE Fighters. As such, it was equipped with a series of innovations over previous models. The practice of designing craft to explicit consumer specifications was one that Sienar would continue with the later Scimitar assault bomber and Aleph-class starfighter. The TIE Defender was 9.2 meters long.
The pilot module was similar to those found in other TIE series fighters, with a ball cockpit and a hatch on the top for entry and egress. The module had room for a single pilot, 65 kilograms of cargo and consumables for up to one week. Like previous TIE models, the TIE Defender lacked life support systems and pilots were required to wear the standard sealed TIE pilot flight suit. However, in a departure from the design of previous TIE models, instead of two parallel wings to either side of the pilot module, the TIE Defender had three quadanium steel solar array wings mounted around an aft section. The rear superstructure contained an I-s4d solar ionization reactor to store and convert solar energy collected from the wing panels. The distinctive triple-wing shape of the TIE Defender led Corran Horn to dub them "trips," and the nickname was also adopted by other Rebel pilots. The wings themselves appeared similar to those found on the TIE Interceptor and TIE Avenger; however, unlike on its predecessors, the wings on the TIE Defender were angled out instead of in. The inclusion of a third wing provided additional solar power to increase the ship's range and the ship's energy management system was designed to allow weapons and shields to be charged with minimum loss of power to the propulsion system.
One disadvantage of the design was an aft blind spot which could potentially be exploited by enemy fighters maneuverable enough to get behind the Defender and which was the cause of some frustration among pilots.
The TIE Defender was one of the fastest starfighters in use during the Galactic Civil War. Although it was based on the standard twin ion engine design, it was upgraded to the entirely new, powerful P-sz9.7 twin ion engine, which allowed it a maximum acceleration of 4,220 G or 21 MGLT/s and a top speed of 144 MGLT or 1,680 km/h in an atmosphere—almost 40 percent faster than a standard TIE Fighter. In addition to the main thrusters located in the aft section, the Defender's triple wing design allowed for three arrays of maneuvering jets—which gave it a maneuverability rating of 110 DPF—and it featured an advanced F-s5x flight avionics system to process the pilot's instructions. When combined, these systems made the ship not only faster, but more agile than any other starfighter in Imperial service and capable of matching the fastest starfighters in the Alliance Fleet.
The TIE Defender also featured a hyperdrive which allowed it to operate independently of capital ships. Testing of the original prototype indicated the need for a more powerful hyperdrive and production models included a class 2, ND9 hyperdrive motivator modified from the version developed for the TIE Avenger. The ship had a Sienar N-s6 Navcon navigation computer with a ten-jump memory.
The TIE Defender's weapons systems were designed to allow it to engage multiple enemy fighters as well as the armed freighters frequently used by the Alliance. It carried a formidable array of weaponry; in standard configuration it had four L-s9.3 laser cannons mounted on the two lower wings and two NK-3 ion cannons mounted on the upper wing. The laser and ion cannons could be set to fire separately or, if concentrated power was required, to fire-linked in either pairs or quartets. The ion cannons could even be fired simultaneously with the laser cannons. Two targeting sensors were located between each pair of cannons to provide the pilot with a constant stream of targeting information. The ship also featured two M-g-2 general-purpose warhead launchers on the bottom of the pilot module, each of which could be equipped with a standard load of four proton torpedoes or concussion missiles. Depending on the mission profile, the ship could be fitted with alternative warheads such as proton rockets, proton bombs, or magnetic pulse warheads. The inclusion of warhead launchers in the design was considered audacious by some members of the design team.
The small tractor beam projector developed for the TIE Avenger could be easily fitted to the Defender. The tractor beam had limited range and could only be used for a short time before stopping to recharge, but it allowed the pilot to temporarily inhibit the mobility of enemy fighters, making it easier to target them with the ship's other weapon systems. Models produced by Ysanne Isard's Defender production facility regularly carried such tractor beams and the technology found other uses, such as allowing TIE Defenders to tow damaged starfighters until they could achieve the required velocity to enter hyperspace. Corran Horn discovered that by using the beam to target a large object, he could effectively use it as an anchor, allowing the TIE Defender to achieve a tighter turning circle.
The ship's defenses were provided by a pair of forward and rear projecting Novaldex deflector shield generators—another advantage over standard TIE models. The shields were designed to recharge more rapidly than in previous Imperial fighters and were nearly as powerful as those found on capital ships, with a total rating of 100 SBD. However, the fighters were not equipped with particle shields, relying on the reinforced titanium hull to absorb impacts from matter. Its hull and wings were the strongest of any TIE series starfighter and were rated at 14 RU.
As with other TIE series fighters, the TIE Defender utilized a wheel and yoke control system. Pulling back would cause the ship to climb, pushing forward would cause it to dive and the ship could be made to bank and turn by twisting the controls. Grips on either side had the weapons trigger switches while an array of buttons and switches in the middle controlled other functions, including throttle, weapons selection and target acquisition. Manipulating rudder pedals caused maneuvering planes to expand or contract to angle engine thrust and quickly alter the ship's trajectory. The ship featured an auto-landing function to plot entry vector and landing speed, although the pilot could retain manual control if they preferred. When not in use, the ship could be left in a password controlled standby mode to prevent unauthorized use.
Various display panels inside the cockpit allowed the pilot to monitor ship's systems and the surrounding area. The main Combat Multi-view Display displayed sensor data on targeted ships while additional monitors displayed short range sensor contacts. Additional panels displayed the remaining charge of weapons, shields and tractor beam systems, current warhead load and power usage. A chronometer was used to display the mission time, or during hyperspace travel to countdown to reversion to realspace. A heads-up display assisted the pilot in aiming the ship's weapons and displayed data from the ship's threat warning system. Like other TIE series starfighters, TIE Defenders were mounted on racks in the hangar when carried aboard a capital ship.
The TIE Defender was in many ways far superior to any other starfighter of the time, capable of outperforming the majority of Rebel starfighters with its combination of firepower, speed, and maneuverability. However, the sophisticated features of the TIE Defender had two major implications. The inclusion of the hyperdrive, shields, and reinforced armor made the ship heavier than any of its predecessors—a fact which made its speed and maneuverability all the more impressive. More importantly, the ship was very expensive, with each unit costing 300,000 credits—more than five times the cost of a standard TIE fighter—or 80,000 credits used. High maintenance and training costs added further to the expense of the fighters.
The TIE Defender was designed to serve as a multi-role starfighter, capable and durable enough to take on a variety of missions. Standard Imperial doctrine recommended that TIE Defenders operate in flight groups of four; however, Imperial commanders took advantage of the starfighter's superior abilities to customize mission forces on a case-by-case basis. Defender pilots often found themselves occupying mission roles previously held by older fighters such as TIE Interceptors and Assault Gunboats.
The TIE Defender's weaponry and deflector shields made it an ideal space superiority fighter, capable of engaging multiple enemies at once. The craft possessed impressive speed promoting its function as a superior interceptor, capable of eliminating incoming starfighters before they posed a threat to Imperial capital ships. Pound for pound each TIE Defender matched or exceeded all Rebel starfighters in speed, armament, defenses, and maneuverability, proving a worthy adversary against even Imperial forces. Their effectiveness against Rebel forces earned them the nickname "X-wing Killers" among TIE Defender pilots and crew.
Their hyperdrives allowed TIE Defenders to conduct patrols across large areas of space without support from capital ships. The versatility of the TIE Defender allowed a large degree of flexibility in its use, as even a single craft could prove formidable, able to outrun or outgun enemy fighters. While on recon missions, Defenders could also bring heavy ordnance to bear on enemy capital ships. Upon the discovery of Grand Admiral Zaarin's plot against Emperor Palpatine, the Sith Lord Darth Vader employed the TIE Defender's abilities in that role, breaking through Zaarin's lines to reach the planet Coruscant. Lord Vader's flight group destroyed the Immobilizer 418 cruiser Harpago, which was attempting to block his imperative voyage.
The TIE Defender's ion cannons paired with the ability to carry multiple warhead types allowed it to function as an effective light bomber or assault fighter. TIE Defenders often assumed missions to disable or destroy enemy installations or capital ships, at times by a single flight group or with only Gamma-class ATR-6 assault transports as support. Defender squadrons could combine their firepower to eliminate a target as large as Alliance Space Stations, while still covering the starfighter interception role.