From Wookieepedia, the Star Wars wiki. A battle droid (also
referred to as war droid, killer droid or clanker) was any droid
designed for combat. There were numerous types of battle droids.
They predated the Galactic Republic by thousands of years, with
the earliest known being Rakatan ancient droids and the war-
robots used by Xim the Despot. Many of the best known battle
droids were those used by the Confederacy of Independent Systems
during the Clone Wars. By the time of the Battle of Yavin,
however, battle droids were extremely rare, most likely due to
the Clone Wars, or because the Empire didn't want an army that
could be easily built and used against it. Types of battle
droids B2 super battle droids precede B1 battle droids into
battle on Geonosis