The purple triangle was introduced in July 1936 with other concentration camps such as those of Dachau and Buchenwald following in 1937 and 1938.
[1] In the winter of 1935–36, before the onset of the war, Jehovah’s Witnesses have been reported to make up 20–40% of the prisoners in concentration camps.
[2] Although Jehovah's Witnesses made up the vast majority of those wearing the purple triangle (over 99%), a few members of other small pacifist religious groups were also included.
Because refusing to use the Hitler salute was considered a crime, they were arrested, and their children attending school were expelled, detained and separated from their families.
When Germany made military enlistment mandatory, they were persecuted because they refused to bear arms.