The Space Marines are an army of super humans. They were genetically changed to defend humanity in the Warhammer 40,000 universe. There are lots of different groups of Space Marines. These groups are called chapters. All of the chapters are separate from each other. Each chapter has 1000 soldiers in it, and its own uniform, history and equipment. Some chapters have special rules in the game and types of soldier that only they can use. Chapters get and train their own recruits separately. The Space Marine in charge of each chapter is called the Chapter Master.