In the 13th century, the many clans of Andor were brought under the iron rule of Krotus. It was in his name that the Andorians spread out from their home to found a dozen colony worlds, as well as conquer the inhabitants of Menk II. Andor and its Andorian Star Empire were ruled by a royal family allegedly descendant from Krotus. In 2137 Andor finally came into contact with Terrans which resulted in a full scale war as the Andorians believed they were destined to rule the galaxy and could not be upstaged by another species.
In the many battles fought, Andor successfully repelled wave after wave of the Terran Empire's ships; however, being short on resources and vastly outnumbered, Andor eventually submitted to the will of the empire, its people given client status and expected to serve the empire.
Throughout the decades of the mid 22nd century, Andor appeared to be a model planet within the empire. Nevertheless, in 2186, during a period of instability for the empire, the Endilev clan stage an uprising whose goal was Andorian independence. Using stolen ships and antique weapons, the uprising was at first successful, but eventually succumb to the empire's might through the efforts of Stephane Louvin. Louvin would use his success in the Andorian campaign to eventually become emperor.
In the uprising's aftermath, a prophetess of the Terionist religion, Umarin, claimed that Louvin was the reincarnation of Krotus. The new faith made Andor loyal to the empire, and its people would go on to play a valuable role in the conquest of the Klingons. Moreover, by the height of the empire, imperial flags would proudly wave and flutter in the streets of Andor's cities and villages. For its devotion and service to the empire, Andor would be elevated to the status of a vassal world. (Decipher RPG module: Through a Glass, Darkly)