Von Bülow was still in school when World War II started. After graduating early from secondary school, he followed the family's tradition and became a military officer. He was deployed to the Eastern Front for three years, serving as Oberleutnant of "Panzergrenadierregiment" 3 in the 3rd Panzer Division. He was decorated with the Iron Cross 2nd class and 1st class. His younger brother, Johann-Albrecht Sigismund von Bülow, was killed on 21 March 1945, less than two months before the end of World War II. Asked during an interview later in his life if he had been a good soldier he answered: "Not good enough, otherwise I would have been part of the resistance on 20 July 1944. But for the dreadful German contribution to world history, I will be ashamed for the rest of my life."