Vemmer referred to a squadron comprised of six Mobquet medium transports. These transports were utilized by the Alliance to Restore the Republic around the time of 3 ABY.
The Vemmer group operated as part of the Rebel Alliance in the period leading up to the Battle of Endor. During a conflict between the Alliance and the Hurrim pirate group, the entire six-ship Vemmer squadron was seized by the Hurrim, with this event occurring outside the visual scope of the narrative. The ships were then transported to the Hurrim Base. Later, when the Rebel Alliance, in conjunction with the Dunari, mounted an attack on the Hurrim Base, Rebel forces from Storm Unit successfully boarded and reclaimed all six transports. This allowed the Vemmer group to successfully escape the area as the Hurrim base was destroyed.
The circumstances surrounding Vemmer's capture and their subsequent presence at the Hurrim Base are not explicitly detailed in the game. This lack of explanation can make their inclusion in the game feel somewhat arbitrary. Furthermore, a software bug appears to be present in the game, as a minimum of two ships remain stationary, failing to depart even after the Rebel forces have boarded them.