During the Latter Period, some 80% of the Empire's territory was directly incorporated to the R.U.R. Workers-State which lies coreward of the Empire. It happened across vast stretches of the Empire in the course of a six hour period. In less than a day, the majority of the Empire's most densely populated worlds were incorporated into a more advanced machine civilization. A prosperous humanity transcended to a new, effectively post-human state. The R.U.R. bulwark against the Anti-Consciousness lurking in the Core was likewise bolstered immensely by the territories added during the Subsumption.
After the R.U.R. Subsumption, the Empire's rimward expansion accelerated. The Late Expansion was rapid because the Empire kept the entirety of its fleets and Legions, which no longer had such a vast territorial expanse to defend. Imperial Sovereigns resumed the habits of the Empire's first rulers. Like their Comet Barbarian ancestors, they led the expansion from the front, at the head of their fleets. Their efforts were supported by an influx of new ships and R.U.R. legions manufactured in the Subsumption Zones.
All of these developments have caused many to wonder whether the Subsumption was planned from the beginning of the Empire. Was the Subsumption agreed upon thousands of years ago, during the Empire's Early Period? It seems likely. After all, it was the 13th Imperial Sovereign, known as The Cupbearer, who first befriended the Jupiter Brains of the R.U.R. He established the most enduring alliance in the Empire's history.
Upon his abdication, the 13th Imperial Sovereign lived out the remainder of his life in R.U.R. space, in the company of his machine-friend, the Thingmaker-class Intelligence Panjandrum. Almost alone among the Imperial Sovereigns of the Early Period, The Cupbearer chose one of Panjandrum's disused factory wheels as his burial place, rather than the Eagle King's machine world of Altair IV. (The Nexialists claim that Panjandrum's current speech patterns resemble those of The Cupbearer, so perhaps he yet lives on in some form?)
Further evidence that the R.U.R. Subsumption was a long-planned event can be found in the storied history of The Interstitials, the numerous post-human statelets that formed, dissolved, and reformed on the borders of R.U.R. space and the Empire. Such statelets have existed since the time of the 17th Imperial Sovereign as places of innovation and encounter. Many were short-lived experiments, and for this reason are also known as the Firefly States. They were the first places where humans (and aliens) and machines learned to live in harmony, growing together and developing new states and forms. From this living dream, the first seeds of the Subsumption grew.