After 6 years of studies, his achievements—a Ph.D. and the teacher’s certificate—let Sommerfeld look confidently to the future. Graduates of the mathematical physics seminar at the University of Königsberg, among whom he now could count himself, normally went on to careers as high school teachers. The teaching certificate qualified him only in the subject matter for this profession, however. Before final qualification, he had yet to complete a probationary year, to demonstrate his practical abilities for a teaching career. But Sommerfeld was in no hurry to move ahead with this. For now, he still had his military obligation to fulfill. As the graduate of a humanistic high school, he belonged to the privileged class who, as “one-year volunteers,” could opt for an abbreviated term of military service instead of the normal 3-year term.