As a 16-year-old, Karel Schummelketel joined the Cadet School in Alkmaar, later continuing his military education at the Royal Military Academy (KMA) in Breda. Departing for the Dutch East Indies in 1920, he served as a cavalry lieutenant and later adjutant until 1928. Subsequently he was posted to the KMA as a riding instructor. His participation at the 1932 Olympics yielded him a silver medal, the Dutch team being one of the two teams to finish the competition with all riders. In the late 1930s, he returned to the Dutch East Indies again, where he was detained during World War II. He returned to the Netherlands in 1950, after Indonesia gained independence. Later, he was a founder and (from 1969-72) head of the Dutch Equestrian Centre (NHB) in Deurne. He was also an author and editor of riding manuals.