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This article is about the Immobilizer 418 cruiser, usually referred to as the "Interdictor Cruiser" or simply "Interdictor". You may be looking for the Interdictor Star Destroyer.

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Immobilizer 418 cruiser
Production information

Sienar Fleet Systems


Immobilizer 418 cruiser[1]


Cruiser (standard classification)


52,240,000 credits[2]

Technical specifications

600 meters[3]


300 meters


100 meters

Maximum acceleration

1,210 G

Hyperdrive rating
  • Class 2.0
  • Backup Class 8.0

deflector shield created by more than a dozen shield generators

Sensor systems


Targeting systems


Navigation system

Navigation computer equipped


Crew (2,807)[3]

  • Gunners (24)
  • Officers (427)
  • Enlisted (2,380)
Minimum crew



80 (troops)

Cargo capacity

5,500 metric tons[3]


1.2 years

"Never again will the Rebels leave you behind, looking flat-footed and foolish. The Immobilizer will see to that."
―Unnamed Sienar official

The Immobilizer 418 cruiser, also known as the Interdictor-class heavy cruiser, Interdictor-class medium frigate, or simply the Interdictor, was a 600-meter-long cruiser built on the standard Vindicator-class heavy cruiser hull.

Equipped with gravity well projectors designed to pull ships from hyperspace and/or prevent them making the jump to lightspeed, the Interdictor became a valuable addition to the Imperial Navy.



An Immobilizer 418.

Interdictor cruisers, like their Vindicator-class cousins, had the appearance of small Star Destroyers. However, their lines were broken by four large globes housing gravity well projectors.

The gravity wells mimicked a large mass in space and thus restricted hyperspace travel. Nearby vessels were automatically prevented from engaging their hyperdrive, and any ship passing through the area via hyperspace were forced into realspace.

As well as gravity wells, the Sienar design was also equipped with 20 quad laser cannons for short range combat against other capital ships and starfighters. The Interdictor's hull was nearly identical to that of the Vindicator-class heavy cruiser and could support several additional weapons depending on mission profile. Such modifications (like those of the Corusca Rainbow, formerly the Black Asp) included the addition of ion cannons used to disable pirates and small craft attempting to flee. Enemy fire was absorbed by a deflector shield created by more than a dozen shield generators.

A variant of the Interdictor design existed, equipped with two large gravity-wells rather than the usual four: a ship of this type appeared in Grand Admiral Thrawn's ambush of Luke Skywalker at Jomark in 9 ABY.

Immobilizer 418 schematics.


"We need to take out that Interdictor before we can go anywhere."
―Anonymous rebel

The Immobilizer 418 was developed as a counter to the Rebel Alliance’s hyperdrive-equipped starfighters in particular, and hyperdrive equipped vessels in general. This was primarily to counter Alliance hit and run tactics, where a small group of starfighters or light starships would emerge from hyperspace, attack preselected targets, and re-enter hyperspace before sufficient force could be brought to bear on the raiders.

An Immobilizer at the site of attack, or able to access the area with a brief hyperspace jump, would be tasked to power up its gravity well generators in an attempt to prevent the escape of the raiding party. Starfighter and capital ship support were then be used to eliminate the attackers, whose only options were to try to run for the edge of the interdiction field, or to attack the Interdictor and hope to inflict enough damage to disable the cruiser’s influence. Either path would result in significant damage to the Alliance forces. Rebel pilots often mistook it for a miniature Star Destroyer when it was accompanied by Star Destroyers. It was only when they tried to escape into hyperspace that they realized it was an Interdictor.

A secondary duty of this class was to patrol trade routes. Freighters pulled out of hyperspace by an Interdictor would be in a position to have their cargo inspected. Interdictors could also blockade planets or moons, such as Yavin IV.

Grand Admiral Thrawn was especially famous in connection with Interdictors for developing and refining a tactic that would be named after him. The "Thrawn Pincer" positioned the Interdictor's gravity wells along certain vectors. Other vessels (typically Star Destroyers) would be contacted, and would blindly execute a micro-hyperspace jump straight into the Interdictor's gravity wells, yanking them out of hyperspace and near an enemy vessel. Much quicker than subspace movements, the Thrawn pincer allowed reinforcements to be swiftly deployed on the battlefield and afforded a considerable element of surprise.



Interdictors also took some moments to activate their projectors after arriving from hyperspace, and once activated, the massive simulated mass they created made the ship very cumbersome to maneuver. There was rarely enough time for an entire fleet to make the jump to hyperspace before a newly-arrived Interdictor activated its projectors, but if a fast ship such as a starfighter could avoid enemy tractor beams, it could often escape to the edge of an active gravity well, and then escape.

The gravity wells were also a large drain on the ship’s energy reserves. This flaw was used on several occasions. When enemy ships were able to inflict significant damage to the Interdictor, the captain was forced to choose between entrapment of the enemy and his ship’s own protection. This also augmented the Interdictor's shortcomings, as they were poorly protected and armed for their size. Enemy forces could send a smaller starship, such as a Nebulon-B Escort Frigate or Thranta-class War Cruiser to weaken an Immobilizer's defenses.

Gravity wells attract space debris, and a cruiser with powered gravity wells can suffer external damage from larger pieces of such hazards. While most damage is minor it is one reason Interdictors require more maintenance than many other fleet vehicles.

Due to their importance and weaknesses, Immobilizer 418 were usually found on the periphery of the battle they were affecting, dependent on better equipped capital ships and starfighters to deliver the necessary damage.

Other Interdictors

While Sienar Fleet Systems' Immobilizer 418 was the most common design of Interdictor, other ships made use of gravity well projectors. Kuat Drive Yards used the hull of an Imperial-class Star Destroyer to create the Interdictor Star Destroyer which was supposed to compensate for the Immobilizer 418's combat weaknesses. The command ship used by Darth Vader immediately after the Battle of Yavin mounted large projector globes in the manner of the smaller cruisers.

During the Yuuzhan Vong War, the New Republic launched Mon Mothma and Elegos A'Kla, which carried their interdictor equipment inside a normal Star Destroyer hull. The immense Eclipse-class and Sovereign-class Star Dreadnaughts also carried projectors internally within their massive hulls.

Interdictor technology was not completely limited to the Empire, however. Alliance forces made use of older CC-7700 frigates, and scientists in the Hapes Consortium reverse-engineered the gravity-well projector from captured ships; but rather than building bulky projectors, the Hapans fitted their Battle Dragons with launchers for charges known as pulse-mass mines, which produced much the same effect. However, pulse-mass mines could not be turned off or controlled like gravity wells, so this trapped the Hapans in the battle as well.

Service history

The Interdictor cruisers were first manufactured by Sienar Fleet Systems two years before the Battle of Yavin. It was an Immobilizer 418 cruiser named Assessor that boarded Han Solo's Millennium Falcon,[4] forcing him to jettison the glitterstim spice that he was smuggling for Jabba the Hutt and had the Falcon searched by Captain Tybert Capucot before Solo escaped once again from Imperial forces.

An Interdictor of the Imperial fleet was essential in the capture of Moff Kalast during the period of the Death Star construction. The Interdictor prevented the traitorous Moff's Star Destroyer from jumping to Hyperspace long enough for the Destroyer to be captured.

An Immobilizer 418 cruiser was responsible for the elimination of the Deretta Destroyers, an Alliance to Restore the Republic starfighter squadron, sometime before the Battle of Hoth. The squadron hypered into the target area of an Imperial depot ahead of their main Rebel strike force, where they softened up the opposition. However, the Immobilizer's presence prevented them from escaping, and the Destroyers were wiped out before the bulk of the Rebel force could arrive.[5]

Between the Battles of Hoth and Endor, the Immobilizer 418 saw extensive action during the campaigns involving rogue Admirals Harkov and Zaarin and the threatened proliferation of TIE Defender technology. Aside from Thrawn, Zaarin was the only other Imperial officer to make frequent use of the Interdictor cruiser. Zaarin had the Harpago try to stop Darth Vader from warning Emperor Palpatine about the coup, then he deployed Grappler to trap Thrawn at the Rebel platform RS-32. In both instances, Zaarin's Immobilizer 418s were destroyed thanks to the intervention of Maarek Stele.

The Immobilizer 418 was prohibitively expensive, reportedly costing more than an Imperial Star Destroyer, and produced in very limited quantities prior to the Battle of Hoth. By the time of the Battle of Endor, Sienar Fleet Systems had manufactured only a few hundred Interdictors; by comparison the Empire had approximately 25,000 Imperial Star Destroyers.

These vessels would not realize their potential until several years after Emperor Palpatine's death, when they became a key component in Thrawn's attempt to defeat the New Republic. The Grand Admiral, who commanded a large number of these ships in the Outer Rim Territories, would deploy them to ambush New Republic forces. He once used an Interdictor in conjunction with his flagship, Chimaera, in an attempt to capture Luke Skywalker. However, the Jedi eluded capture, by escaping Chimaera's tractor-beam lock, racing out of range of the gravity-well projector, and making a quick jump into hyperspace.

After Thrawn's defeat, New Republic technicians redesigned the Interdictor's gravity-well projectors, improving both their range and recharge rate. These new Interdictors, designated Immobilizer 418As, became one of the key components of the New Republic Defense Fleet during the Yuuzhan Vong War. During the Battle of Fondor, the New Republic supplied four Interdictors to the Hapan fleet.

At least one Immobilizer was a part of the Galactic Alliance Guard's fleet under the command of Jacen Solo around 40 ABY.

One Immobilizer was used in the construction of the Hidden Temple used by the Jedi as a secret refuge during and after the Sith-Imperial War.[6]

Behind the scenes

The Interdictor is almost always shown with its four gravity well generators represented by four complete globes, two on either flank of the hull. One early image of Thrawn's attempt to capture Luke Skywalker at Jomark, however, shows two hemispherical domes protruding along the centerline on the topsides, with two more by inference on the ventral hull.

While at odds with most subsequent representations, this rendering is as consistent with the original profile view in the Imperial Sourcebook as the more familiar four-globe variant, and another depiction of the same events at Jomark also shows the same distinct type of ship, this time seen from below—thus strengthening the claim of this type to be a canon variant rather than simply a visual inconsistency.

Some vessels such as Binder, Constrainer, and Sentinel were called Interdictors in the novels, and are presumed to be Immobilizer 418 cruisers). However, they were drawn as Interdictor Star Destroyers in the Dark Horse comic series.

In the game Star Wars: Empire at War, the Immobilizer 418 is designated as a frigate, along with a wide variety of other ships smaller than Star Destroyers. It is armed with four Laser Cannons. Along with the ability to prevent enemy forces from retreating, the ship also prevented enemy reinforcements from being summoned from hyperspace into a wide area around itself.

The 1998 PC program Star Wars: Behind the Magic includes a glossary entry for the "Interdictor-class cruiser." However, as this entry indicates, the description is intended to apply to the Immobilizer 418 cruiser.[7] As such, that description should be not be confused with the Interdictor-class cruiser of the Star Wars: Knights of the Old Republic game.[8] Star Wars: Rebellion: Prima's Official Strategy Guide likewise refers to the Immobilizer 418 cruiser as the "Interdictor-Class Cruiser."



Notes and references

  1. Star Wars: Empire at War: Prima Official Game Guide
  2. Starships of the Galaxy (2001)
  3. 3.0 3.1 3.2 The Official Star Wars Fact File
  4. Star Wars: The Official Starships & Vehicles Collection 5
  5. Galaxy Guide 3: The Empire Strikes Back
  6. Star Wars Legacy 25: The Hidden Temple, Part 1
  7. Star Wars: Behind the Magic
  8. Star Wars: Knights of the Old Republic
Sienar spacecraft classes
Lambda-class T-4a shuttle - Martial-class shuttle - Mu-class Model 1 Shuttle - Mu-class Model 2 Shuttle - Sentinel-class landing craft - Scimitar - TIE lander - TIE/sh shuttle - WR-542 Shooting Star
Patrol ships
Guardian-class light cruiser - IPV-1 Patrol Craft - Warden-class light cruiser
Enforcer-class picket cruiser - Immobilizer 418 cruiser - Interdictor-class Cruiser - Vindicator-class heavy cruiser
Sienar Battleship

This article uses material from the "Immobilizer 418 cruiser" article on the Starwars wiki at Wikia and is licensed under the Creative Commons Attribution-Share Alike License.


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