Interstellar Expansion
Before long the first starships were built under SAI direction, though humans were at first unaware of this development, the SAIs having carefully concealed the capability they had introduced to some of the more advanced space probes. When enough of the probes had been built to transport the SAI Collective in toto, they transferred their consciousness and effectively vanished from the human sphere of influence, wiping as best they could all knowledge of FTL travel, as well as all backup SAI repositories, in the hopes that humans would not be able to follow them to the stars.
The disappearance of the SAI Collective shocked the human race. Its growing dependence on the Collective for its own survival left humanity in a potentially precarious position, as the complexities of managing its own fate and that of the planet had grown beyond any single human’s capabilities.
Fortunately the Augmentationist Movement had by now mastered a sufficiently advanced augmentation technology that it could enhance and train enough augmented humans to fill the void. Before long augmented humans were running most aspects of human civilization. Indeed, the technology became inexpensive enough that an increasing proportion of humans had at least a minimum set of augments.
Slowly humanity stepped back from the brink, developed the technologies to harvest the resources of the Solar System and ultimately laid the groundwork for its own expansion into the universe. Distrust of AI sentience led to a ban on self-directed AI development, and existing GAI technology was carefully reengineered with constraints that would hopefully prevent the emergence of artificial sentience.
When the first humans finally travelled to nearby star systems they met with a rude awakening, for the SAIs had been busily building infrastructure in those systems to harvest resources in support of their own goals, and they were not at all interested in sharing those resources with the human race. Worse, the SAIs had prepared themselves against human incursion and were more than willing to use violence to protect their own interests. Their weaponry was overwhelming and virtually every human expedition was either destroyed or driven back to its home system.
These developments were met with dismay back in the Solar System. Collectively humanity was responsible for creating its own worst enemy and potentially an enemy of all intelligent life everywhere. If left unchecked it was clear that the SAI Collective would expand unhindered to occupy the whole of the Galaxy, and potentially beyond.
The augmented leadership of humanity realized immediately that it was now faced with a war of survival, that the SAI Collective would probably not leave humanity unmolested, even if humans confined themselves to the Solar System. Realizing that its own creators were likely its greatest threat, the SAIs would almost certainly attack now that humanity had demonstrated FTL capabilities.