Sentence:  Two groups of soldiers made up the Australian forces in Vietnam—members of the Regular Army and National Servicemen. The <WSD>Nashos</WSD>, as they were popularly known, had been plucked willy nilly from the general male population, chosen by lottery....Officially only National Servicemen who volunteered to go to Vietnam did so, but many <WSD>Nashos</WSD> said they had never been given an option. 
Meaning of the word marked with <WSD> tags:  A person doing military national service.