Final answer:
The Ku Klux Klan (KKK) originated as a social fraternity for Confederate veterans in 1866, which evolved into a violent vigilante group. The second iteration of the Klan was established in 1915, influenced by media and pseudo-scientific eugenicist ideas, expanding its targets beyond African Americans to include Jews, Catholics, and immigrants.
Step-by-step explanation:
The organization that served as a basis for the formation of the Ku Klux Klan (KKK) was itself the original KKK, founded in 1866. This early incarnation of the Klan emerged in the aftermath of the Civil War as a fraternal order of Confederate veterans in Tennessee, spearheaded by former Confederate General Nathan Bedford Forrest. The name 'Ku Klux Klan' is believed to be derived from the Greek word kuklos, meaning circle.
The first Klan started as a secretive social fraternity but quickly devolved into a violent terror group, aiming to maintain white supremacy by terrorizing African Americans and their allies, and undermining the Reconstruction efforts. Paramilitary white-supremacist organizations like the KKK used violence as their primary weapon, with vigilante tactics such as intimidation, property destruction, assault, lynchings, and murders.
Despite its initial disbandment, the Klan saw a resurgence in the early 20th century. The Second Ku Klux Klan was established in 1915, influenced by the film Birth of a Nation and the eugenicist writings of figures like Madison Grant, which promoted white supremacist ideas and warned against the dilution of white, Protestant heritage in America. This new Klan expanded its animus to include Jews, Catholics, and various immigrants, becoming a significant force in American society during the 1920s.