In Hitler's Shadow War, World War II scholar Donald M. McKale contends that the persecution and murder of the Jews, Slavs, and other groups was Hitler's primary effort during the war, not the conquest of Europe. According to McKale, Hitler and the Nazi leadership used the military campaigns of the war as a cover for a genocidal program that centered on the Final Solution. Hitler continued to commit extensive manpower and materials to this "shadow war" even when Germany was losing the battles of the war's closing years.