The fourth horseman : one man's secret mission to wage the Great War in America by Robert L Koenig

"This story has never been told before in full. And Dilger is a fascinating analog for our own troubled times. Having thrown off the tethers of obligation to family and country, he became a very dangerous man indeed: A spy, a saboteur, and a zealot to a degree that may have so embarrassed the German High Command that, after the war, they ordered his death rather than admit that he worked for them." - Editorial Reviews