Complex sentence: Forrest was an early member of the Ku Klux Klan ("KKK " or"the Klan") which was formed by veterans of the Confederate Army in Pulaski, Tennessee in 1866 and soon expanded throughout the state and beyond.
Split into simpler sentences: Forrest was an early member of the Ku Klux Klan (KKK). The KKK (the Klan) was formed by veterans of the Confederate Army in Pulaski, Tennessee in 1866 and soon expanded throughout the state and beyond.