It is from the book “The Last 100 Days” by John Toland. He was a reporter during WWII and said his book is based on “several thousand primary sources”.

Russia intelligence services have been producing conspiracy theory propaganda from even before the Communist era. Adolf Hitler was radicalized in 1909 to hate Jews by “The protocols of the Elders of Zion”. That’s right, he killed 6 million Jews because he bought into Russian bullshit.