Pre Vizsla publicly served Duchess Satine as the governor of Mandalore's moon Concordia, but was really the leader of the Death Watch, a secret society of Mandalorian commandos who sought to overthrow Satine's government and reclaim the Mandalorians' honor as warriors.
Vizsla and Count Dooku plotted to assassinate Satine, which would lead to a Republic occupation of Mandalore. Vizsla's Death Watch would then liberate the planet, joining the Separatist cause.
Things did not go according to plan, and Vizsla and Dooku bitterly parted ways. Death Watch became a group of nomadic warriors, with the formerly manicured and orderly Vizsla becoming unkempt and battle-worn as their leader.
Though outwardly loyal to Duchess Satine, Governor Pre Vizsla secretly hated everything the woman stood for. Vizsla honored the warrior past of the Mandalorians, and wanted to return the planet to its war-like ways. He secretly led the Death Watch from the moon of Concordia.
When the Jedi Council grew suspicious of Mandalore after the discovery of a Mandalorian saboteur in their shipyards, Obi-Wan Kenobi was sent to investigate. He uncovered the Death Watch plot and dueled with Pre Vizsla.
Mandalore has a long, strife-torn history. In the past, armored warriors dominated the planet's affairs, but the world's relentless campaigns of conquest ruined the planet. Duchess Satine Kryze was part of a new movement to rebuild their world in an era of pacifism, but Pre Vizsla worked behind-the-scenes to ensure the old ways didn't die quietly.
Death Watch was a radical splinter group of Mandalorians unhappy with the current direction of their planet. Pre Vizsla was their secret leader, who used his position as Governor of Concordia to further their cause.
Count Dooku recognized Death Watch as a tool he could use against the Republic. He helped supply Pre Vizsla, earning the loyalty of the mercenary group in exchange for help in overthrowing the government of Duchess Satine.