In 1915, composer Alfredo Casella returned to Rome after living in France for many years. He joined the staff at the Liceo Musicale and wished to modernise Italian music as a result from his travels. Despite showing little interest, Respighi had a small involvement in Casella's new organisation, the Società Italiana di Musica Moderna. When Italy entered World War I in May 1915 Respighi, aged 36, was eligible to join the army, though his position at the Liceo Musicale granted him temporary exemption from military service. After a holiday in more peaceful surroundings for the summer, Respighi returned to Rome to continue teaching. One of his new students in his fugue and composition class was Elsa Olivieri-Sangiacomo; the two started a relationship and Elsa, fourteen years his junior, married the composer in January 1919. Their friend, librettist Claudio Guastalla, spoke of their marriage: "It functioned on an almost transcendental level of human and spiritual harmony."