As a newly promoted officer, in 1916 the 20-year-old Heinse was dispatched to the Italian Front of World War I. He served as part of the 43rd Infantry Regiment and fought at the Isonzo, taking part in the battle of Doberdò, San Martino del Carso and Monte San Michele. The horrors of war shaped Heinse as a pacifist, and it was at the time (1916–1917) that he published his first poems. He would send his poetic works, complemented by articles, to newspapers in the Banat that would publish them. Major influences on the developing writer were Hermann Hesse, Rabindranath Tagore, Romain Rolland and later Rainer Maria Rilke, whom he also met in person. Heinse's earliest works authored during World War I were later republished by the independent Viennese literary magazine "Das Tage-Buch". Years later, in 1937, he would publish these in Sofia in a book of poetry titled "Der brennende Berg" (“The Burning Mountain”).