The Alpha Contracts were the first contracts signed by human mercenary companies. Exactly 100 units formed from elite military units and contractors such as Blackwater left Earth to fulfill these contracts.
Of those one hundred units, only four survived. Through a quirk of fate, all four had horses in their logos. These four, Cartwright’s Cavaliers, Asbaran Solutions, Winged Hussars, and the Golden Horde, became known as the Four Horsemen.