Born in what was later Slovakia, Bela De Nagy competed in team sabre for the US at the 1936 Berlin Olympics, while represented the New York Athletic Club. De Nagy attended school in Budapest and at the Austrian-Hungarian Naval Academy in Fiume. He received an electrical engineering degree from the Royal Hungarian University in Budapest where he then became an assistant professor. During World War I he was a pilot and first officer of the Navratil scout squadron. He was credited with shooting down several enemy planes and was decorated four times.
De Nagy began fencing in 1909 under maestro Italo Santelli (#22737) in order to be prepared in case he was challenged to a duel but he enjoyed the sport and so continued after learning the basics. He won the intercollegiate championship of Austria-Hungary three times. He became a member of the Board of Governors of the Hungarian Fencing association. De Nagy emigrated to the United States in 1924 and was one of the engineers who designed the electrification of the Penn railroad between New York City and Washington.
United States