Age of Strife

In the fictional Warhammer 40,000 universe, the Age of Strife is the name for the chaotic period of human history between the 25th and 30th millennia.

According to the "official" histories of the Imperium, the precise details and dates of the Age of Strife are not known, due to having been lost over vast amounts of time, to the chaos of that period, and partly to censorship by various Imperial authorities.

Causes and Beginning
At some point during the 25th millennium, humanity was nearing the end of a period of great success, the so-called "Dark Age of Technology"; this meant that human-kind had reached its technological peak. The "Standard Template Construct", or STC, had been perfected by human scientists and was being used on a large scale. Despite an apparent lack of central authority, humans inhabited vast portions of the galaxy, and their civilization was largely free from difficulties with external factions- namely, other races. This success was about to come to an end.

At that time, the ancient Eldar Empire began its decline; the great success of the advanced Eldar race had led to decadence and hedonism on a great scale. This rampant corruption, which would eventually cause the Chaos God Slaanesh to be born, led to a great increase in Warp Storms. Parts of the galaxy inhabited by humans became isolated by these storms, leading to revolts and civil wars. Many human-inhabited systems also became prey to unfriendly alien forces, such as the Orks.

However, by far the worst event of this period for humanity was the spectacular rise in the occurrence of human mutation, especially the mutation leading to psykers and the psychic powers they wielded. Prior to this, humans had had little experience in dealing with the forces of the warp, and the unexpected appearance of humans who could draw upon its energies led to riots, witch hunts and lynchings. Many psykers themselves were driven insane, either by the great power they suddenly possessed, or by the fear of persecution (or both).

Many psykers were overwhelmed by Chaos entities, and were possessed. These possessed psykers, as well as other selfish (or insane) psykers who learned to control their power, would cause even more havoc, leading to mass hysteria and devastating wars. Horrific weapons invented previously during the era of technological achievement were unleashed, turning verdant worlds such as Baal Secundus into barren, radiated desert planets- or worse.

In a relatively short span of time, the galaxy-spanning human civilization was brought to its knees, and was forced to endure nearly five millennia of terror, war and slavery. Other than tales of great suffering, little information has survived this dark time.

Earth and Mars
Control of the Sol System shifted constantly between Earth, Luna and Mars during the first half of the Age of Strife. By the 28th Millenium all traces of civilisation on Earth were long gone; instead, techno-barbarians battled one another over the scraps of the ancient culture. Little information remains from this dark time, but it is known that tyrants such as Kalagann of Ursh (northern Asia/Russia), Cardinal Tang, and Narthan Dume of the Panpacific Empire ruled during this age. According to the novel Horus Rising by Dan Abnett, Dume was opposed by the Yndonesic Bloc, while the Urals remained a centre of industry.

Mars underwent a very different transformation. After brief anarchy, the tech-priests of the Adeptus Mechanicus emerged victorious over the mutants and unified their homeworld. The tech-priests then visited Earth but were appalled at the destruction there and saw nothing worth saving. Instead, the Martians studied the warp and after many lifetimes learned to detect 'lulls' in the warp storms. At the same time the immense fighting machines known as Titans were created.

For over a thousand years the Cult Mechanicus watched and waited. Whenever a break in the warp storms occured, an expedition was sent, complete with a full Titan Legion and thousands of servitors and tech-priests. Some of these expeditions were lost in the warp or died on faraway worlds. Others succeeded in establishing 'Forge Worlds' - replicas of Mars. Broken messages were transmitted to Mars, but not until the time of the Great Crusade that the Forge Worlds and Mars would be reunited.

The End of the Age, and the Rise of the Emperor
Eventually, an immensely powerful human leader (and psyker) known as the Emperor divined that the final birth of Slaanesh was nearing, as well as the effect this birth would have. He made preparations for this galaxy-changing event; he gathered military forces, began his conquest of Earth, and started the processes necessary to create his genetically tailored super-warriors, the Primarchs and the Space Marines.

Upon the birth of Slaanesh sometime in the early 30th millennium, the crippling warp storms were swept away (which allowed for easier galactic travel), the Eldar race was nearly annihalated, and the Emperor began to carry out his plans to reunify humankind under his rule. With the Emperor's ascension, the Age of Strife was finally over and a new age had begun. This brief age of conquest, heroism and unity would be known as the Great Crusade, and it would in turn end with the tragedy of the Horus Heresy.

Legacy
The Age of Strife had an immense impact on human civilization. Humanity barely survived the period, and most of the knowledge of the previous golden era was lost, much of it irrevocably; in particular, the loss of the STC system is seen as a serious setback for the advancement of the Imperium. The Adeptus Mechanicus constantly searches for STC technology, and jealously guards what little it finds— in fact, it treats the STC as holy, virtually worshipping it. This focus on re-attaining and worshipping the ancient STC rather than inventing new technology, as well as the centralization of this knowledge in the hands of the Adeptus Mechanicus, has led to a stagnation of Imperial science.

Humanity as a whole became more superstitious and distrustful, something which the Imperial government goes to great lengths to encourage. In particular, the Imperium distrusts mutants, aliens and psykers; this distrust runs so deep that the Imperium has a complex secret police force, known collectively as the Inquisition, devoted to finding and destroying all aliens, daemons, mutants, unsanctioned psykers and "heretics" (anyone deemed to be straying from official Imperial doctrine) existing within the Imperium. Despite the general distrust of psykers, many critical functions of the Imperium, notably the maintenance of the Astronomican, are performed by them, so they are often rounded up by Imperial agents and forced into service. The Adeptus Ministorum, the official religious hierarchy of the Imperium, enforces a strict dogma including absolute devotion to the Emperor (who is treated as a god), closed-mindedness, xenophobia, and blind dedication to one's duty.

In short, the authoritarian Imperium of Man is the way it is in large part due to the great suffering endured during the Age of Strife.