The B-series battle droid represents a heavily manufactured series of battle droids that were widely deployed by entities such as the Trade Federation, their associated partners, and the Confederacy of Independent Systems, with their most significant engagement occurring throughout the duration of the Clone Wars.
During the Clone Wars, the B-series droids served as the main combat unit for the Separatist Alliance, acting as the opposing force to the clone army of the Grand Army of the Republic. Before the Clone Wars era, these B-series units achieved considerable recognition through their deployment in events such as the Battle of Naboo, in addition to various other conflicts.
A vast number of B-series battle droid models belonging to the Separatist Alliance were deactivated during the mission to Mustafar; however, a portion of these droids continued to function, either due to being reprogrammed or by other means.