A warlord was a military leader in charge of civilian territory. The Confederacy of Independent Systems made use of several warlords including General Grievous, who plotted to blockade and occupy planets such as Ryloth. Other Confederate warlords were Archduke Poggle the Lesser of the Stalgasin hive and the Karkarodon Riff Tamson.
Kaplan was an Imperial warlord. Following their major loss in the Battle of Endor, which saw the first death of Galactic Emperor Sheev Palpatine and destruction of DS-2 Death Star II Mobile Battle Station, the Galactic Empire shattered into factionalism. After its fall in the Battle of Jakku, the once centralized empire was reduced to scattered warlords and mercenaries. While most of those warlords publicly vowed to restore the New Order to its former glory, many were in fact more interested in carving fiefdoms out of the Empire's wreckage.
In the years after the fall of the Galactic Empire, Moff Gideon and Grand Admiral Thrawn were considered warlords in the eyes of the New Republic. Approximately three decades after the Battle of Endor, Kylo Ren severed his ties with the Jedi Order and became a warlord of the First Order.
Within Star Wars canon, the position of warlord first appeared in the 2002 film Star Wars: Episode II Attack of the Clones through the character of Poggle the Lesser, who was confirmed to be a warlord in the opening newsreel for the Star Wars: The Clone Wars episode "Weapons Factory." Additionally, the audio description for Attack of the Clones available on Disney+ incorrectly translates a quote from Poggle to be that he is sending his "warlords" to hide in the Geonosis catacombs. The film's subtitles instead state Poggle is saying he is sending his Geonosian warriors to the catacombs.