Prior to the entry of Italy into World War I, Lussu joined the army and was involved in several skirmishes. As a complementary officer of the Sassari Infantry Brigade in 1916 he was stationed on the Asiago Plateau. The brigade had arrived on the plateau in May 1916 to help in the Italian effort to stop the Austrian Spring offensive. In the month of June 1916 the brigade conquered Monte Fior, Monte Castelgomberto, Monte Spil, Monte Miela and Monte Zebio. After the war Lussu wrote the book A Year on the High Plateau (Un anno sull'altipiano) about his experiences of trench warfare on the Plateau. The 1970 movie Many Wars Ago (Uomini contro) by Francesco Rosi is taken from this book.