- "This is the Garden of Kadesh. For thirteen generations we have protected it from the unclean. The Turanic Raiders who came before you refused to join and were punished for this trespass. Like theirs, your ship has already defiled this holy place. If you have come to join we welcome you and will spare your ship until all have disembarked. If you have come to consume the garden you will be removed at once." — Kadeshi Ambassador
The Kadeshi were originally Hiigarans prior to and during the Exile. After the Hiigaran Empire collapsed at the hands of the triumphant Taiidan Empire, the future Kadeshi along with the rest of their people were sent away from Hiigara after the Taiidan were persuaded to spare the survivors. When the Hiigaran convoy ferrying them to the Outer Rim came to the Great Nebula, at least one vessel broke off and sought shelter in the nebula, thus founding the Kadeshi race. The Kadeshi developed in isolation after growing in both strength and numbers later began to prey on ships passing through the Nebula. The Kadeshi called the Nebula the "Garden" and it eventually became the center of their religion, having served as a place of sanctuary and allowing them to thrive as a people once more. An important tenet of this religion is that any outsider ship coming into the Garden defiles it, and therefore, the intruding ship's crew has only two choices: to join the Kadeshi or be destroyed. So strong is their belief in their religion that they prefer to sacrifice themselves rather than allow anyone to leave their holy place.
The Kadeshi built large needle-shaped motherships and developed hyperspace inhibitors to capture and prevent ships from leaving the nebula. They also designed small but maneuverable starfighters that could literally swarm and overwhelm their enemies through sheer numbers. They proved to be great warriors, and eventually even the Taiidan came to fear the Great Nebula. According to the Bentusi - no one returns. Eventually, in the face of this unseen threat, the rest of the galaxy shuttered all shipping lanes passing through the nebula, leaving the Kadeshi as the dominating force and left relatively undisturbed for generations to come.
During the Homeworld War, the Kushan first encountered the Kadeshi when the Kushan fleet burst into the Nebula while on their way to find their Homeworld, dodging their enemy as the Kadeshi themselves had several millenia before. Having already begun to harvest the rich resources within the nebula as they attempted to orient their sensors, the Kushan had already violated the sanctity of the Garden. Their presence prompted the Kadeshi to approach, and sent their ambassador to personally greet the Kushan. In this meeting, the ambassador informed them of their trespass onto their holy space, having already dealt with the Turanic Raiders who had similarly trespassed into the Garden only a short time before the Kushan's own arrival. The Kadeshi then offered the Kushan the chance to join them in the safety of the nebula, and that they would be removed if they continued to consume the Garden. The Kushan explained that they meant the Kadeshi and their revered space no harm, and would withdraw immediately back into neutral space. At this point, the Kadeshi informed them that there is no withdrawal from the Garden, and then proceeded to launch a massive assault to exterminate the intruders.
Unlike the Turanic Raiders and many other intruders, the Kushan Mothership and her fleet managed not only to repel attacking Kadeshi fighters, but also began to strike at the Kadeshi Mothership, eventually forcing it to retreat. During this attack, the Kadeshi Mothership had employed an inhibitor field to sabotage the Kushan's attempt to jump into hyperspace. Through this, analysis found that the Mothership's hyperdrive signature was identical to that of the Khar-Toba, the ancient vessel that had ferried the Kushan to Kharak after the Exile. This prompted suspicion of a deeper connection between the Kushan and the Kadeshi, the first hint towards their shared ancestry.
As the Kushan fleet moved deeper into the Nebula, the Kadeshi deployed two more Motherships for support and they trapped the Kushan Mothership in an inhibitor field while their fleet surrounded the invaders. Again, the Kadeshi offered the Kushan the chance to join them.
- "Again we offer you a chance to join us and live here in peace." — Kadeshi Ambassador
- "We cannot stay - we're on a journey. But let there be peace between us, for we have something in common. The hyperdrive technology left to us by our ancestors is identical to yours. The Homeworld we seek may be yours as well." — Fleet Command
- "You will fail. The evil that drove us here will find and destroy you. From you they will know about us and come here. This cannot come to pass." — Kadeshi Ambassador
In response, the Kadeshi sent most of their ships in massive waves and attacked the Kushan fleet from all directions. They sent in multiple waves of fighters supported by their powerful Multi-Beam Frigates, the later of which arrived in several formations with the purpose of destroying the Mothership itself with their devastating force of ion cannons. However, the Kushan fought back using their Multi-Gun Corvettes supported by Drone Frigates that proved to be a match against the fast, but lightly armored Swarmers. They also proceeded to destroy the Kadeshi's lightly armored Fuel Pods to deny their fighters the ability to refuel on the field, while also capturing or destroying the Multi-Beam Frigates razing their forces. Eventually, the Kushan attacked the Kadeshi's motherships one by one, destroying two of them even as the fast-moving warships attempted to ram the oncoming Kushan ships in self-defense. Facing defeat, the Kadeshi retreated to a wreckage of an ancient ship, possibly the very one that first brought them to the Nebula. From this discovery the Kushan deduced that they and the Kadeshi were indeed of the same race, their ancestors having parted ways amongst themselves as they traveled across the galaxy. The Kadeshi continued to fight desperately but were finally defeated by the Kushan, disrupting the inhibitor field and allowing the Kushan to exit the nebula.
With the conclusion of the battle, it is assumed that the Kadeshi were rendered extinct due to the Kushan infiltration.
- For the majority of the series, the Kadeshi were never named and only treated as the "Protectors of the Garden". As of Homeworld Remastered, they have been officially named as the Kadeshi.
- Debate remains over the assumed extinction of the Kadeshi, with many speculating that others of their civilization continue to survive elsewhere in the nebula and from the fact that their annihilation was never conclusively confirmed. Nevertheless, the Kadeshi have not been heard from since their defeat.