The Battle of Montmusart was a major conflict that occurred during the course of the First Expansion War. It was fought between the Gonian Ascendancy, aided by the Blue Sun Pirates, and the Vesperian Hegemony. It took place on the lush, tropical world of Montmusart. The Gonian Ascendancy's leader, Nadir Jahan, hated the leader of Vesperia, Rhulain Arkham, for supporting a rebellion in Gonian territory. After the rebellion was put down, the Gonian Ascendancy decided to assault Montmusart, a key world in the .