Theodore Kaufman published Germany Must Perish! in 1941, advocating the genocide of the Germans through the sterilization of all Germans. Louis Nizer, in What to Do with Germany, published in 1944, disagreed with mass sterilization but wanted collective punishment: https://en.wikipedia.org/wiki/Germany_Must_Perish!
Following World War II there was the Morgenthau plan (ultimately abandoned at the 11th hour), to deindustrialize Germany, leading to the extermination of 40 percent of its population: https://en.wikipedia.org/wiki/Morgenthau_Plan; http://www.fpp.co.uk/bookchapters/Morgenthau.html.
