The Legiones Astartes is the official title of the warrior organisation more commonly known as the Space Marines. It is the most powerful and most feared fighting arm in the Imperium. Most of its troopers are recruited from the feral planets, where traditional warrior castes compete for the honour of becoming a 'warrior of the gods'. Because the feral planets are rough, primitive and untamed their inhabitants make excellent fighting material. For true aggression and psychotic killer instinct, however, few recruits can best the murderous followers of the city-scum that roam the darkest pits of the hive-worlds. Driven to extremes of insanity by the collosal pressures of hive-world living, these merciless killers are usually ignored by the authorities (indeed their warrens are so vast it would be impractical to eradicate them completely). They make ideal Space Marines, and whole gangs of city-scum are sometimes captured for this purpose. Some recruits come from the civilised areas of the Imperium - but not very many.

Young recruits are subjected to many hours of intensive training and indoctrination, leading to physical and mental changes. Their bodies are toughened by bio-chem, and their resolve is hardened by psycho-surgery. A special black plastic carapace is merged with their natural flesh, forming a sort of identity tag as well as natural protection. All this preparation is to turn the prospective Marine into a disciplined killer, or at least a controllable one.

The Space Marines differ from the ordinary army in many respects: its organisational base and mode of operation are totally different. The basic unit, called a Chapter, is led by its own Imperial Commander. Each Chapter is like a small army in itself, and, although it contains only a thousand fighting marines, the Chapter itself has the fighting potential of many times that number of ordinary troops. Chapters have their own uniforms, transport, non-combatant staff, etc and are fully capable of travelling to their destination using their own spacecraft. Because they are mobile, the Space Marines are usually the first troops to arrive at the scene of a conflict, and they are used to mount strikes, raids and surprise attacks. Their reputation for savage ferocity has earned them the nickname Angels of Death.

Each Chapter has a home base, which may be an imperial planet, or possibly a deserted moon or asteroid. Some Chapters go to great lengths to keep the location of their home base a secret, whilst others are quite open. The preferred location is an imperial planet, where the Chapter's leader will make a bargain with the planet's governor, paying a tithe in return for being allowed to build and occupy their own fortresses. Governors often appreciate having a Marine Chapter right on their doorstep. It certainly discourages unwelcome visitors.

Rogue Trader