Occurring between 1209-1211, the Curtain War was waged between the forces of the Black Imperium, independent vampire fleet factions, and the combined forces of the Ziru Sirkaa, the Regency, and the Reformation Coalition.
After securing its spinward border with the Treaty of Corridor, the Vilani government believed the time was right to reclaim the Iridium Throne and restore the Ziru Sirkaa as the rightful ruler of the Imperium. A Ziru Sirkaa Capital Fleet was assembled and set course for Capital. It met little resistance until it reached the information void known as the Black Curtain, whereupon the fleet was outmatched by the Black Imperium Navy.
Not content with driving off the invaders, the Black Imperium sent several fleets out to annex its neighbors, demanding immediate surrender or suffer its wrath. These fleets ultimately made their way into Ziru Sirkaa territory to exact revenge.
Recognizing the threat posed by the Black Imperium, High Regent Caranda chose to send a fleet to aid the Vilani. Better to fight the enemy in Vland Sector than risk the lives of Regency citizens. However, the decision proved unpopular as many had not forgiven the Vilani for their unprovoked attacks from 1205-1208. Ultimately, the Regency factionalized and soon found itself in the midst of civil war.
While preoccupied with a sudden surge in vampire fleet activity, the RCES nonetheless provided valuable intelligence to Regency and Ziru Sirkaa forces. These independent vampire fleets would eventually ignore the Reformation Coalition altogether and focus their efforts on the worlds hidden behind the Black Curtain.
After a crippling defeat following the Scouring of Vland, the remaining Black Imperium's fleets were forced to retreat homeward to defend its worlds.