The Trade Federation made these as a succesor to the OOM-Series Battle Droids. They were made to resemble the skull of a Nemoidian, and a body of a Geonosian to be intimidating. They were programmed into a Central Computer inside of a Federation Ship known as a Droid Control Ship. The Federation made them profitable, but at a very cheap price.When Darth Sidious began to use the Trade Federation to attack Naboo, the Federation deployed hordes of OOM's on the planet, and overwhelmed the palace of Theed, with support from Droidekas, STAPs, AATs, MTTs and PACs. During the invasion however, their lack of independant thought was used against them by two Jedi Knights who broke in to rescue the queen of Naboo.
Then OOMs then fought in the Battle of Grassy Plains, and overwhelmed the Gungan Army with their numbers. However, their Control Ship was destroyed during the Space Battle of Naboo, and they deactivated, giving the Gungans an untimely victory.
After the Battle of Naboo, the Trade Federation relocated to Geonosis after joining the Separatist movement, and replaced the OOMs with B1s with independent minds, because of what happened during the Battle of Grassy Plains on Naboo.
Eventually OOM's saw action again during the First Battle of Geonosis, but with the improved B1s. But in the First Battle of Geonosis, which started the Clone Wars, they were defeated by the superior Clone Army.
Over the course of the Clone Wars, the B1s started going through changes, such as a high pitched voice, for unknown reasons. The B1s eventually were made the main foot Soldiers of the CIS. They participated in numerous battles, such as the Battle of Muunilist, where they were defeated. They gained some victories, such as the Battle of Hypori, with the help of their commander General Grevious.
Eventually, many of them were deployed on Kashyyyk, and thousands of others defended Felucia, Saleucami, and Mygeeto. They eventually lost Saleucami, and Felucia, but held out on Mygeeto, and pressed their attack on Kashyyyk. Eventually, the CIS Headquarters known as Utapau was attacked, and General Grevious was killed, but the B1s continued the fight.
However, after the Separatist Council was executed by Darth Vader, the war turned, and the B1s lost every other battle. They were then deactivated by Darth Vader, which ultimately ended the war.
During the reign of the Empire, some B1s were reactivated again. A couple of them were activated by renegade Jedi on Jaguada, and were used to fight off some Stormtroopers. Others were activated by the Empire to serve as brief Security Guards.
Over the years, one former Separatist member named Gizor Dellso reactivated the B1s to rebel against the new Galactic Empire. They were defeated at their base of operations on Mustafar however, and Dellso was killed, which ended the brief conflict.
Lots of more conflict between B1s followed. Many were still activated, and got into brief skirmishes between Imperial Troops. Others were used for sport, such as when Jawa Crimelord Witten competed with Hutt Crimelord Jabba Desilijic Tiur in a Demolition game.