A Brief History of Death Watch
Death Watch— Kyr’tsad
Struggling with their participation in the Ithullan genocide, some Mandalorians desired a change from the warrior-clan ethos of the past. This desire was seized upon by Jaster Mereel resulting in the development of his Supercommando Codex upon his ascension as Mand’alor. His followers were renamed the “True Mandalorians”, but the concept of acting as honorable mercenaries did not appeal to many who preferred practices of the past. Under the leadership of the merciless fighter Tor Vizsla, warriors united to form Death Watch; a splinter group whose goals were to return Mandalore to its warrior roots while conquering the galaxy. Inevitably, fighting occurred between the two groups leading to a Mandalorian Civil War.
After numerous battles which swung the tide of victory from one group to the other, Mereel was ultimately killed by Vizsla on Korda 6. Death Watch moved on to conquer other domains, but was never forgotten by a foe whose family was killed in the civil war: Jango Fett. The last remaining True Mandalorians rallied under Fett, naming him the new Mand’alor. Death Watch and Fett’s Mandalorians met on Galidraan, where the Jedi were unwittingly tricked into destroying the remaining True Mandalorians, and killing all but Fett who was later sold off as a slave. The original incarnation of Death Watch came to an end when a liberated Fett me Vizsla on his ship over Corellia and ended his life. The few remaining Death Watch scattered across the galaxy and many believed the group had met its end.
While working with the Kaminoans as a template for the Grand Republics Clone Troopers, Jango Fett brought in one hundred trainers (of which seventy five were Mandalorians) to develop and elite clone commando group. Two of the Mandalorians, Isabet Reau and Dred Priest, secretly trained some of them under the precepts of Death Watch. Their plans were discovered by Fett, and put to an end, although practitioners survived by operating under the principles of ba’slan shev’la, or “strategic disappearance”. After Fett’s death during the Battle of Geonosis, Death Watch returned under the guidance of Pre Viszla, the governor of Concordia, a moon of the planet Mandalore.
Source: Wookiepedia Death Watch Entry