The Seed:
Shortly after Arcturus Mengsk (Emperor Arcturus I) took control over the Confederacy and claimed Himself Emperor of all the Terrans the transition was swift and decisive. The last vestiges of the Confederacy were relegated to insurgent groups spreading false propaganda against the Emperor. Mere weeks before He would make public His plans to eliminate the Protoss presence from the Koprulu sector, brothers from earth under the banner of the UED arrived and attempted to retake control of the Terran colonies they left so long ago. The Emperor, not willing to give into the evil the UED represented, mustered an army of Marines and began transferring the Empire's blooming economy from that of trade to that of war. The conflict (known as the Second Civil War) was short-lived, however, as the UED's massive armada made quick work of any Imperial army unit to resist the new balance of power. In a last-minute request for aid, Arcturus I asked for any assistance against the flood of UED Marines and battlecruisers. Some historians say that our Emperor did not expect what was to come. We know better. The former aide to our Emperor had been captured by the Zerg and transformed into the hideous Queen of Blades. She had been fashioned to be the successor to the Zerg Overmind, and when the Protoss destroyed it, she ascended into her place of power. Having received our Emperor's message requesting support, she rushed to Korhol to see what aid she could give to help quell the UED threat (Imperial Intel tells us that the UED planned to domesticate the newly-forming Overmind to serve their demented will.) She saw the ruins of the First Empire, and vowed to help us rebuild and avenge ourselves on the UED. After several hit-and-fade assaults and a few direct skirmishes, we retook Korhol and several of its major satellites. Then Kerrigan turned on us, destroying our fleet and military capability. She said this was for "abandoning her" when the Zerg overran our position the fateful day we lost her. The Emperor was enraged for a week. Then He established basic structures and started doing recon for three weeks. Then He sent SCV teams into the Dead Sea three weeks. And then he disappeared for three weeks. It is said that he spent his seclusion in the hidden library of Korhol, reading the ancient texts of Terran Religion and History, from which the basic ideals of the Imperium now grow and flourish.
The Nourishment:
The restructuring took two-and-a-half months, but when the Emperor returned from the seclusion, He seemed to lose the fiery rage He had before He left. In its place was a haunted look that to this day sends shivers down the spine of any that would look into it. Rather than speak of petty revenge, Arcturus I gave inspirational speeches speaking of "manifest destiny" and "crusades" using the litany of those ancient texts He had been absorbed in. During His rise to popularity, word reached Him that the Zerg had beaten the Protoss back into an alternate dimension and desired no less than Earth itself. He knew that Earth, being such an inconsequential planet geographically in the galaxy, was to be taken to demoralize humanity throughout the cosmos. "This," said the Emperor, "must not be allowed to happen." We all knew that Arcturus I had become a changed man since the seclusion, and now that the threat had been made to all Mankind, something had to be done... and so the plans of cleansing began.
The Revelation:
Arcturus I was a genius and a visionary. He knew that the Zerg had their own advantages and that the Terrans could not match them evenly and hope to win. Even when the Sons of Korhol were but a terrorist organization, Arcturus had conscripted the finest of geneticists and scientists to work on genetically enhancing human performance well beyond their known limits. Arcturus' labor bore fruit and the first genetically superior Terran was "born". This new Terran was 3 times faster stronger and smarter than the average Terran. For Arcturus, this was a gift from "God". These new Terrans would bear new units into his army of Terran crusaders and their first mission was to liberate their home from the Zerg scourge. Dozens of Dropships slipped through the Zerg swarms and delivered the equipment and plans for the saviors of humanity. Soon the legions would be revealed. The Initiation of the Imperial Space Marines: While the basic front-line Marine fought and died for the new Second Empire, Arcturus I was monitoring the production of the first 100 "new" Marines. After they were all created, He drowned them in Zerg blood, but their alternate respiration system activated and they walked out of the tank baptized in the blood of their mortal enemies. "This," the Emperor announced to his advisors, "is the Death Company, whom I love." He soon released the Death Company across hundreds of worlds, each time the battle report came back to him: Congratulations! You are victorious! No Casualties. With great joy in His heart, the Emperor signed the order to conscript a new batch of Marines, launching phase II of his plans.
The Liberation:
Time passed and word reached the Emperor that all hope was lost: Earth was captured and held under siege. On the fringes of the Milky Way, Arcturus I had secretly built the largest Armada ever assembled in Terran history. It cruised towards Earth with 1000 legions of the new "space marines," as well as the now legendary Death Company. The Armada used an abandoned Protoss Fleet Beacon and managed to "teleport" themselves one way back to Earth local space (Note: this has never been replicated and is hailed as a miracle by modern accounts). With the Zerg at their strongest, the Armada held the line as well over a million ships and mobile command centers made their descent to the planet. For 5 days the chapters fought a defensive war, their mineral deposits and vespene geysers depleting with each passing hour. Then the wraiths and battlecruisers broke atmosphere, a scene long known as the Great Reinforce. Yamato cannon loads hammered the nearby hatcheries and creep colonies while cloaked wraiths descended in droves upon Overlords, demolishing the Zerg recon capability. Within a month the Arcturus I himself planted the flag of the Second Empire on the ancestral home world of all Humanity. The Marine Chapters had eradicated the entire infestation with notable losses. However, the entire Death Company had been destroyed in the offensive. Earth had been liberated and thus begins modern history...
The Imperium:
Many lessons were learned by Arcturus I. The Terran forces would be split into the Imperial Guard and the Imperial Marine Chapters (IMC). The Imperium Space Marine Chapters would be 1000 chapters, with 1000 men per chapter. They would be the fists of the Emperor and God. The IMC would cleanse the universe for the Terrans and wage a modern crusade against any to cross the will of the Emperor. The Imperial Guard would inhabit and garrison all such liberated territories. Never again would foreign forces settle in Terran space. This excerpt from Arcturus I speech to Terra Prime and all Terran colonies citizenry on the day of the Liberation is hailed as the beginning of the Imperium. " My fellow Terrans, we will no longer be suffered unto these horrors by foreign powers again. Let there not be strife by the color of our skin, the name of our Gods, the heritage from which we are from... for we are all humans and as such we are all one. The Broods of the Zerg and the Tribes of the Protoss have had their way with us and no longer shall they know this again. It is time that we embrace our destiny as the chosen race of the universe and cleanse that which is evil... That which is not Terran. God has given us a great gift and we shall embrace it and forge ahead to a new Empire, an Empire for humanity."
The Crusade:
Immediately following the liberation of Terra Prime, the chapters of the IMC were sent in all directions to liberate or destroy any Protoss or Zerg infestations. The chapters to this date have liberated and or destroyed over 500 planets and continue to grow and spread... ever vigilant on their crusade for Humanity.
For the Emperor