Cloaking technology was first encountered by Humanity when the NX-01 begun its mission in 2151. Species which used cloaking devices included the Suliban1, Xyrillians.2 and Romulans.3 The NX-01 herself managed to capture a Suliban Cell ship in the first days of her mission1, and her crew were subsequently able to use the device during a rescue mission after Captain Archer and Lieutenant Reed were captured whilst visiting a pre-warp civilisation.4
In 2152 Archer was given information by Daniels which enabled him to penetrate the cloaking devices of the time using a pair of quantum beacons. Archer used the beacons to locate a Suliban stealth cruiser and obtain evidence that his ship had not in fact been responsible for the destruction of a Paraagan mining colony shortly before.5 The quantum beacon technology made the cloaking devices of the time largely obsolete, and the technology fell into such disuse that by the mid 23rd century a practical cloaking device was considered a virtual impossibility as light would have to be bent around a cloaked object, something which was theoretically possible but would require an enormous amount of power.6
Nevertheless, the Romulan Empire was able to develop such a device and employ it on one of their warships 2266. The vessel crossed the Neutral Zone and attacked several Federation outposts with a high power plasma torpedo weapon, destroying them completely. Although the ship was able to cloak itself from sight at will, the Enterprise found that it was still visible to motion sensors - though these were not accurate enough to give more than a very general location, insufficient for a firing solution. Although the cloak was quite effective, it did have other drawbacks. The power drain was so great that the Romulan vessel was unable to use its own scanners effectively and could not fire any weapons whilst cloaked. The vessel also had relatively limited range due to the high fuel consumption.6
The Romulans apparently traded cloaking technology to the Klingons in exchange for warships. Certainly the Romulans began operating Klingon-designed vessels by 22687, while the Klingons were known to employ cloaking technology at least as early as 2285.8 The Klingons made at least one major innovation in cloaking technology in 2293, when they produced a Bird of Prey capable of firing torpedoes whilst cloaked. The prototype vessel battled the USS Enterprise and USS Excelsior in orbit of Khittomer; despite emitting large amounts of neutron radiation the ship was highly effective, but the Enterprise crew realized that the Bird of Prey could be tracked by following the plasma exhaust emitted by its engines and modified a photon torpedo to follow this trail.9 The development was so effective that the Klingon development was rendered next to useless, and was never again an effective combatant.
In 2311 the Federation signed the Treaty of Algeron, which reaffirmed the Romulan Neutral Zone and forbade the Federation from developing or deploying any cloaking technology.10
Perhaps the most impressive example of cloaking technology was observed in 2364, when the supposedly mythical planet of Aldea was discovered by the Enterprise-D. The planet had been hidden for centuries behind a complicated light refracting mechanism which bent light around it in a similar manner to the Romulan cloaking device.11
The Minosians were also known to employ cloaking technology as part of their Echo Papa 607 weapons system. The Enterprise-D was forced to battle a cloaked drone weapon in orbit of the planet; it overcame the cloaking device by luring the drone into the atmosphere where the turbulence made it visible.12
Later in the same year the Romulan D'Deridex class Warbird was encountered for the first time when the Enterprise-D met one at the Neutral Zone. It was initially believed that the Enterprise sensor systems could detect the Warbird through its cloak, but it quickly became apparent that the Romulans had in fact deliberately allowed themselves to be detected in order to determine the Federation's intentions towards them.13
Subsequent encounters revealed that the improved cloaking device still suffered from limitations. The Romulan vessels remain unable to fire whilst cloaked, whilst advances in Federation sensor technology have made the invisibility of a Romulan Warbird less than assured.14 Perhaps the most effective development was the Tachyon detection grid; created by Enterprise-D personnel in 2368, the system involves a network of vessels which send tachyon beams towards one another across a large area of space. Even a cloaked vessel will disturb one of these beams when crossing it, hence rendering it detectable.15 Subspace listening posts and gravitic sensors are both a worry for Romulan commanders, and the Federation has deployed large numbers of these along its borders.14
In 2369 the Federation gained significant intelligence on the Warbird when a Starfleet officer masqueraded as a Romulan for a short time. She confirmed that the ship must keep a careful watch over its own electromagnetic missions whilst cloaked, and that the radiative emissions of the warp engines must be precisely balanced by means of nullifier cores. Even a small misalignment in one of these cores creates a polarized magnetic disturbance whenever the ship is in motion, something which can be detected by a Federation vessel.14
By the mid to late 24th century cloaking technology was widespread enough that even private citizens could obtain it on occasion, though usually such devices were inferior to the military models. In 2367 a confidence trickster masquerading as Ardra, a figure from Ventaxian mythology, used an inferior copy of a Romulan cloaking device to hide her ship from the Enterprise-D. The ship was eventually detected by a wavelength stretchout.16 In 2370 Quark was able to obtain a handheld cloaking device suitable for a small transport ship, something which is highly illegal in Bajoran space. Although the device was in less than perfect condition, Natima Lang was able to use it to escape DS9 whilst evading Cardassian observation. 17
Ironically, perhaps the greatest single advance in cloaking technology was made by the Federation. In 2358 the Starship Pegasus was believed destroyed after a mutiny by the crew. However, in 2370 Starfleet discovered that the Pegasus was still largely intact. Admiral Pressman, Captain of the ship at the time of its loss, attempted to recover some technology from the vessel using the Enterprise-D. It transpired that certain Federation officers had been illegally developing a Phase Cloak, a device which could change the structure of matter in order render it both invisible and able to pass through normal matter. A vessel equipped with such a device could hide within a planet or a star, completely immune from conventional attack. The crew had been so fearful of what they considered to be a dangerous device that they had mutinied rather than continue to operate it.10
In 2368 the Enterprise assisted a Romulan vessel in distress, and discovered that this vessel had also been attempting to test a phase cloak. The results had been disastrous, causing an accident that would have completely destroyed the ship if not for the assistance of the Starfleet vessel.18 There has since been little sign of progress with this technology.
In 2371 the Romulans agreed to allow Starfleet the use of a single cloaking device on board the USS Defiant in order to facilitate that ship's missions against the Dominion, in return for all of Starfleet's information about the organization.19 Although the original agreement was to only use the cloak in the Gamma Quadrant, Captain Sisko subsequently violated this rule on many occasions.20
In 2379 the Romulans fielded a new vessel, the Scimitar. An exceptionally powerful warship, the Scimitar was equipped with a new generation cloaking technology which rendered it completely invisible to the sensors of the Enterprise-E. The Scimitar was able to both use shields and fire whilst cloaked. The cloak also remained effective even through multiple weapon hits from phasers, photon and quantum torpedo hits and disrupters. This indicates that the balance of technology has again shifted in favour of the cloaking device, at least for the present.21 There can be little doubt that this will inspire the Federation to begin working on a new generation of even more sophisticated sensor systems.
In the Mirror universe cloaking technology was also developed by the Suliban, and a Suliban cloaking device was also captured by the NX-01. Lieutenant Tucker was able to hook the cloaking device into the ship's power grid, allowing the ISS Enterprise to cloak itself and infiltrate Tholian space in 2155.22