The Andromedans were first sighted by the Federation in 2277. The ship was codenamed Intruder and positively identified as having come from the Andromeda galaxy. The ship was seen to only be there as an observer, a pattern that was to follow in the singular appearances of the Andromedans in Federation space for the first few years. The Andromedans had no known relations with any other race, a fact that apparently never changed since.

By 2282 the sighting had increased, causing Starfleet Intelligence to task more assets to finding out what they could about these mysterious visitors. Attempts at First Contact were spurned, adding to the concern. Four years later in 2286 saw a disturbing change in the behaviour of the Andromedans; the ships were now attacking ships on sight in a random pattern across the Beta Quadrant. Starfleet raised the alert status and prioritised learning about these now-hostile intruders.

There were raids conducted by various ships labelled by Starfleet Intelligence. In 2294 a ship codenamed “de Medici” conducted raids in both Federation and Kzin space. These attacks were initially blamed on a possible breach of the Treaty of Sirius by the Kzin, until more accurate details of the culprit came to light. In 2298 a ship codenamed “Machiavelli” raided Gorn space. In 2299 the “Giovanni Sforza” placed bases in Federation, Gorn and ISC territories. This fact was not clear for over three years. In 2300 a ship codenamed “Cesar Borgia” raided Federation and Klingon space.

The change came in 2301. With raids having weakened and disorganised the Beta Quadrant powers, the Andromedans initiated a full scale invasion of the Beta Quadrant. The Romulans, Gorn, Lyrans, Hydrans and, especially, the ISC were hit hardest by the invasion. The Andromedan ships would arrive in squadrons of up to three ships, although usually operated in single units. These ships possessed technology that made them almost impervious to all known weapons systems. The ships had Power Absorption Panels that swallowed the kinetic energy damage from weapons fire. The tractor-repulse weapon literally shook enemy vessels to pieces, with no need to drain shields.

By 2303 the Federation border was penetrated by the Andromedan forces, met by elements from up to a third of the fleets. The initial attacks on nations further afield were analysed by experts from Starfleet. The Andromedan ships appeared to attack quickly, overwhelm the opposition and then disappear rapidly before friendly armadas could respond. In 2306 the means of the rapid deployment and exfiltration was discovered by scout vessels. The Rapid Transport Network was the means by which the Andromedans could move their ships quickly, making their ships appear more in number that they actually were.

2308 saw the Andromedans at the height of their power, reducing many nations to a fraction of their sizes. A plan was formulated to hamper the Andromedans by destroying their RTN. Within a year this strategy had hamstrung the enemy invasion attempts. The Andromedans had to concentrate their efforts on maintaining their territorial gains. During all the entire time a living Andromedan was never seen; their invasion forces used sophisticated robots to conduct their boarding, ground assaults and occupational forces.

There were three versions of robot used by the Andromedan Invaders. The General Purpose Boarding Robot (GPBR) with two pincer manipulators, occasionally with 3 or 4. This version had 4 phaser emitters and armour known as Andromedan Plastic Armour- thought to be a laminated metal-plastic that shields most effectively against weapons fire. The Andromedan Scout Robot (ASR) was a small flying droid that was there to scan silently- the stealth features being almost unsurpassed. The scout was armed with a mono-filament whip which sliced organic threats and lightly-armoured structures. This droid is also protected by Andromedan Plastic armour. The Heavy Weapons Robot (HWR) which was the primary assault robot. The mission: destroy. This robot has five 3-yard long tentacles and a tractor-repulse weapon which can melt metals, shatter crystal, rend metal apart and splatter flesh and blood. This weapon was discovered to only have ten shots before the robot needed to return to base to recharge. This made the deadly weapon something only used when necessary. The robot walked on four legs, making it unable to sneak attack. Finally the robot was protected with Andromedan Chrome armour, a hyper-polished substance probably force field-enhanced material even more effective against weapons fire.

The Andromedan occupational forces included scientific bases; what these bases were researching on or doing, this fact was never established.

The Klingons and Federation unified their efforts against the Andromedans under the co-operative treaty agreed between the Federation President and Chancellor Azetbur; this was signed during the ISC Pacification Campaign. This alliance was successful in liberating captured territories and driving the Andromedans back. The Andromedan actions were lessened rapidly, allowing the Romulans to quickly recover their capabilities and increase their hostilities with the Federation. The Federation discovered that their Ulysses class dreadnoughts and Ark Royal class carriers, successful designs used in the ISC campaign, proved to be effective against the Andromedans. Construction of both was accelerated to meet the Andromedans and bring the invasion to a swift end.

The final assault came with the discovery of the primary Andromedan Invader base in the Lesser Magellanic Cloud. Chancellor Kaarg, successor to Azetbur, honoured the previous alliance and sent their main battle fleets to assist in the destruction of the base. With the destruction of the primary base the invasion was over; sightings of the Andromedans since has been rumoured only, no confirmed encounters have been made.

In the aftermath, unlike with the Interstellar Concordium there were no war crimes trials as no living Andromedan was ever seen or captured. Organic material was obtained from debris from destroyed ships. The ships and robots always self-destructed to stop technology from being passed on to the enemy. All that was taken from the decade of invasion and occupations were the experiences and improved technology and tactics developed to counter the threat.

The Interstellar Concordium subsequently re-affirmed that their Pacification Campaign of 2294 – 98 was inspired by the Organians as a means to bring the divergent races of the Beta Quadrant together “to face a larger threat in the future”. They argue that the Andromedans were this larger threat. This argument is extended to become a justification for the actions of the Interstellar Concordium. This case is rejected on the grounds that a simple message from the Organians, as they did before, would have had the same effect without the loss of life. The ISC counter this by reminding the Federation that the Organians were enigmatic and were not there to reveal the future. The case is still ongoing.