Warhammer 40k Timeline: From the Age of Strife to the Indomitus Crusade

Warhammer 40,000 has a long and tangled history, and most of it comes in fragments. This guide walks through the major eras in order, from the deep past to the present-day setting, and points to the archive’s posts on each. Dates in the setting are counted in millennia, so M31 is the 31st Millennium. Where sources disagree, this guide sticks to the broad strokes rather than guessing at exact years.

Before the Imperium: Old Powers and the Dark Age of Technology

Long before humanity’s empire, older races fought over the galaxy. The Necrons were once a mortal people who traded flesh for metal and then slept for ages, while the Aeldari built a vast and psychically gifted civilisation. Humanity spread through the stars in a technological golden age, working alongside thinking machines until those machines turned on their makers. The Aeldari empire, meanwhile, collapsed through its own excess, an event remembered as the Fall.

The Age of Strife

Violent warp storms then cut human worlds off from one another. Without contact or trade, civilisation fractured. Many planets fell to war, mutation and superstition, psychic powers became feared and dangerous, and even Terra was carved up between rival warlords. It was a long, dark stretch with few records, and much of what is known is reconstructed after the fact.

The Emperor and the Great Crusade

Out of that chaos came the Emperor. He first united Terra in the Unification Wars, then set out to reclaim humanity’s lost worlds in the Great Crusade. To lead the effort he created the Primarchs, superhuman sons who were scattered across the galaxy as infants and rediscovered one by one. Each took command of a Space Marine Legion, and together with the Mechanicus of Mars they pushed the borders of the new Imperium outward.

The Horus Heresy

Horus, the most trusted of the Primarchs, was named Warmaster and then turned on his father, taking roughly half the Legions with him. The war opened with the atrocity at Istvaan III, the treachery at Calth followed, and the fighting ended at the gates of the Imperial Palace on Terra. Horus was killed, but the Emperor was gravely wounded and placed on the Golden Throne, where he has remained ever since.

Reconstruction and the Age of the Imperium

In the aftermath the surviving Legions were broken up into smaller Chapters to make another civil war harder, a reorganisation guided by Roboute Guilliman’s Codex Astartes. The Imperium turned inward, its bureaucracy and its church grew into vast institutions, and the worship of the Emperor as a god became the dominant creed. Over many centuries it settled into the rigid, sprawling state the setting is known for.

The Age of Apostasy

In the 36th Millennium, religious and political power became tangled together in a period of tyranny and bloodshed. Its end brought reforms that limited the church’s authority over the wider government, and it left a lasting mark on how the Imperium treats its priests and their armed orders.

The 41st Millennium: A Galaxy at War

By the 41st Millennium the Imperium was fighting on every front at once. The Gothic War saw Abaddon’s Black Legion strike deep into the Imperium, Ork warlords launched huge invasions such as the wars for Armageddon, and the young T’au Empire began to expand. The Tyranids arrived from beyond the galaxy and ravaged worlds in the Tyrannic Wars, while the Necrons slowly woke on world after world.

The Great Rift and the Indomitus Crusade

At the end of the 41st Millennium the Black Legion’s final push led to the fall of Cadia, and a huge warp storm known as the Great Rift tore across the galaxy. It cut the Imperium in two and plunged much of it into darkness. Around the same time Roboute Guilliman returned, and the Indomitus Crusade was launched to bring the scattered worlds back together, backed by a new generation of Space Marines known as Primaris.

That is where the setting stands today: a vast, battered empire with a living Primarch at its head, and a galaxy full of enemies. To follow any of these threads in depth, the Reading Order lists every series, and the Faction Index sorts the archive by faction.

Author

Librarian

The Librarian keeps the long view of the 41st Millennium: the wars, crusades and turning points, the institutions of the Imperium, and the books and games that tell its story. Expect timelines, campaign histories and patient deep dives into how this grim galaxy actually works.

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Librarian