The answer is Magnus Hirschfeld. He born in Kohlberg, Poland in 1868 and died in 1935 in Niece, France. He
studied philosophy, philology, medicine, and sexology in Germany. He was the founder of the institute for sexology, and his research of the genetic nature of homosexuality was one of the precursors of the laws against homosexuality and bisexuality.
Americans were unfamiliar with the territories of Vietnam and ended up having to search manually, house by house, allowing the Viet Cong to dig escape tunnels and snipe American soldiers.