Guido Mazzoni's son was taken prisoner in World War I; in exchange, Mazzoni offered to volunteer, and at the age of 56 was given a post of lieutenant in the famous Italian Alpine Corps in 1915. He was promoted to captain in 1917, and saw some of the most grueling action of the war in the Alps. Notice the triangular Alpine hat in the photograph commemorating Mazzoni's eightieth birthday: it was standard uniform for the Alpinisti.