The Nimbosa Crusade was an Imperial Crusade undertaken in 993.M41 by the Black Templars, Imperial Fists, Raven Guard, and Ultramarines Space Marine Chapters against the Tau Empire following the Tau conquest of the Civilised World of Nimbosa. All of these Chapter have reputedly fought the Tau on the heavily contested planet at one time or another and the world has changed hands many times. When Hive Fleet Kraken began to threaten worlds on the Eastern Fringe of the Imperium of Man in 992.M41, the High Lords of Terra responded by stripping the worlds on the border with the Tau Empire of Imperial forces. The Tau Empire was quick to recognise this redeployment and soon moved to take advantage, beginning the period of Tau history known as the Third Sphere Expansion. The Tau had soon annexed a w