Why Is It Ironic That Paul And His Comrades Refer To Themselves As "Stone-age Veterans" When They Compare Themselves To The New Recruits?

Meaning 'In the West Nothing New' in German, this 1928 novel by Erich Maria Remarque, a German veteran of World War I describes the German soldiers' extreme physical and mental stress during the war, and the detachment from civilian life felt by many of these soldiers upon returning home from the front.