The massive SD-9 was equipped with laser-reflective armor, ionization shielding, powerful servomotors, and advanced targeting sensors. In place of hands, the SD-9's forearms supported a heavy repeating blaster and an explosive plasma cannon. This droid was rumored to be more than a match for a hundred infantrymen. The SD-9 was also fitted with an ionization shield generator.
During the Thrawn Crisis in 9 ABY, SD-9s were used by the New Republic in limited amounts. In 10 ABY, during the reborn Emperor Palpatine's insurrection, the Empire retook Balmorra and all the remaining SD-9s were sold into the Imperial arsenal. The Emperor also assigned Umak Leth—the creator of the World Devastators and the Galaxy Gun—to work with the Balmorran engineers. They would produce the even deadlier SD-10 battle droid, which would be used against the Empire.
Following the Emperor's second death at the Battle of Pinnacle Base, the Balmorrans rebelled. The Emperor then sent his Executor, Sedriss QL, to crush the revolt, thus resulting in the Battle of Balmorra. During the battle, the SD-9s were outmatched by the more advanced SD-10s. The Balmorrans also unleashed their new X-1 Vipers. This was to counter-act Sedriss' Shadow Droids. This resulted in a draw between the two factions.
- The Essential Guide to Planets and Moons
- The Essential Guide to Droids
- Arms & Equipment Guide
- The New Essential Guide to Characters
- The Official Star Wars Fact File 43 (MIL7-8, Military Droids)
- The Complete Star Wars Encyclopedia (As "SD-9 infantry droid")
- Scavenger's Guide to Droids