Things you don't learn in history class or hear about in the news. German-American concentration camps in the United States, during WWI and WWII.
https://history.nebraska.gov/blog/marker-monday-german-pow-camp
http://ss.sites.mtu.edu/mhugl/2016/10/19/camp-hindenburg/
https://mungfali.com/post/9176678CC1477D87A6D8A11B695A16E990BDDA2F
https://mungfali.com/post/AE4B828096C352AB252BAED30AFD5B84581D7DFD