The Galactic Padishah Empire encompassed the entire Known Universe of humanity at the time. It was also commonly referred to as the Imperium, and later as the Old Imperium.
While the Padishah Emperor was seen as the supreme ruler of the Known Universe, control of the Known Universe was shared, in a quasi-feudal arrangement, by the Landsraad, the Bene Gesserit, and the Spacing Guild. However, during Paul Muad'Dib's Imperial reign (and even more so during the reign of his son, the God-Emperor Leto II), the level of political power held by the Emperor increased drastically.
The Imperium referred to the form of absolute trans-world governance used to maintain control of the Known Universe, typically before the rise of Leto Atreides II. It provided a socioeconomic and political framework within which the Faufreluches class system operated.
For more than 10,000 years the Imperium was headed by a ruling family or noble House, namely House Corrino. The Corrinos used political power and the superior force of its army to coerce or manipulate other significant political players such as the Bene Gesserit, the Spacing Guild, the Bene Tleilax, and the Landsraad.
The Imperium managed function through a delicate balance. The Emperor's military force was matched only by the sum of all the Lansdraad forces, and the Bene Gesserit, Bene Tleilax and the Spacing Guild provided services of their own. In this way, those that remained in power had to rely on others, otherwise the Imperium would fall into chaos.
Most economic ventures were conducted through CHOAM, the company in which the Imperial House, the Landsraad, and Bene Gesserit and the Spacing Guild all had a stake.
The Imperium came into being some time before the rise of the Thinking Machines. However, its more widely known structure only emerged after the Butlerian Jihad. For several thousand years it was governed by House Corrino, the ruler of whom took the title of the Padishah Emperor of the Known Universe, since the Imperium spanned millions of planets over several galaxies.
In 10,193 House Atreides took control of the Imperium through Duke Paul Atreides, who became Emperor and successor to Shaddam Corrino IV. Upon Paul's death, control passed briefly to his younger sister and Imperial Regent Alia Atreides.
After Alia's death, control of House Atreides, and thus the Imperium, passed to Paul's son Leto II. However, Leto's totalitarian form of rule saw a radical shift in the balance-of-power and structure of the Imperium.
Over the course of 3500 years, Leto's rule saw many changes to imperial society. Among these were:
- the shift to an all female imperial army; although house guards (aka national guards) were still allowed to use males;
- the dilution of power of the Great Houses, and a significant reduction in their numbers;
- populations forced to become almost entirely system-bound;
- the erosion of the Fremen way of life;
- the partial outlawing of Mentats;
- the end of Wars of Assassins;
- the shift in ownership of the Bene Gesserit breeding program to the Imperial Seat;
- a significant increase in the use of Ixian technology by the Imperial Seat;
- the death of the Faufreluches system.
Many more longstanding imperial institutions disappeared. The last vestiges of the Imperium effectively ended shortly after Leto's death, when The Scattering saw a mass exodus of humanity into uncharted space. The Imperium, the form of government that had kept humanity together for nearly 15,000 years, ended when Leto II plunged to his death into the Idaho River from a bridge far above.
Essentially, the remnants of the Imperium were inherited by Leto's Fish Speaker army, which appeared to continue to exist (although in a largely bastardised form) more than 1500 years after Leto's death. The planetary systems and galaxies within its borders were commonly referred to as the Old Imperium from that time onward. However, some institutions were not gone for good; approximately 1500 years after the death of the Imperium, Great Houses began to re-emerge from obscurity.
Behind the Scenes
After Leto's death, there appeared to be at least some planets within the Old Imperium that maintained their own form of government without Fish Speaker Involvement, such as Gammu which appeared to be under the control of the Bene Gesserit.