The Sentinel droid-series (also known as the war-droid or military droid-series) was the only known series of android among the war machines used by the Galactic Republic and the Sith Empire in the Jedi Civil War. Variants included the Mark I, Mark II, Mark III, Mark IV, and Mark V, which were all outwardly identical. The HK-series was based on the Sentinel line in design and structure.
During the Mandalorian Wars, Revan's Republic forces deployed such droids from KT-400 military droid carriers, from which they controlled them by remote signal much like the Droid Control Ships of the Trade Federation and the Confederacy of Independent Systems millennia later. Such droids were used when the Republic conquered the Mandalorian remnant on Dxun. At least one carrier crashed on the moon's surface; it and its complement of droids were later discovered by the Jedi Exile.
The Ahto City Civil Authority used these droids extensively for the purposes of security and apprehending those who broke the laws of Ahto City. Revan was apprehended on Manaan by a battalion of sentinel droids under the command of a Selkath officer. Like the Mark IV assault droid, the sentinel droid was preferred by the nonviolent, pacifistic Selkath over live soldiers.
- Star Wars: Knights of the Old Republic: Prophet Motive
- The Betrayal of Darth Revan
- Star Wars: Knights of the Old Republic (First appearance)
- Star Wars: Knights of the Old Republic II: The Sith Lords