The Ultramarines are considered one of the strongest and most honored of all the Space Marine Chapters in the Imperium of Man and were responsible for almost single-handedly holding the Imperium together after the Horus Heresy. Highly disciplined and courageous warriors, the Ultramarines have remained true to the teachings of their Primarch Roboute Guilliman for 10,000 standard years. The Ultramarines were originally the XVIII Space Marine Legion before the reforms that initiated the Second Founding and reshaped the Imperium after the Heresy on the orders of Guilliman himself. The Ultramarines are one of few Space Marine chapter that is loyal to the Alliance of Nations, along with the likes of the Salamanders and Raven Guards, as the other chapters joined the Imperialist Alliance during the Second War.