The term droid tank or tank droid referred to any type of tank that operated without the assistance of a live crew. Much like droid starfighters, they were operated through the use of a droid brain; these could either be independently-controlled or governed by remote interface with a tactical computer; in this way they were much like ordinary battle droids and their starfighter counterparts. Tank droids were utilized throughout the history of the galaxy, from the Old Sith Wars to the Yuuzhan Vong War.
The Tank Droid Mark IV was a class of huge, bipedal and self-propelled droid tank. It was heavily armed, carrying a rocket launcher, blaster cannons, a grenade launcher and a flamethrower within its blocky chassis. They were primarily used for facility defense against intruders, overwhelming them with firepower.