Reinhard entered the army in 1909. When the war began, he served with an artillery regiment on the Western Front. Badly wounded in November 1914, he did not return to the front until June 1915. After completing flight training, he was wounded for the second time in December 1915. Returning to duty in February 1916, he served with FA(A) 205 before being assigned to FA 28 in the Balkans. In 1917, Reinhard attended Jastaschule and was assigned to Jasta 11 on 24 June 1917. Scoring his first victory on the morning of 22 July 1917, he shot down English ace Geoffrey Cock over Warneton. On the morning of 4 September 1917, he was wounded in action for the third time. After recovering from his wounds, he assumed command of Jasta 6 on 26 November 1917. With the death of Manfred von Richthofen, Reinhard assumed command of JG I on 22 April 1918. In July 1918, he attended the aircraft trials near Adlersdorf. After Hermann Göring finished test flying a Zeppelin-Lindau D.I, Reinhard took it up for a test flight but was killed when a strut broke and the top wing collapsed.