As for the trilogy: My guess is that the three songs of Bogle on the First World War are meant by that (and not one of the Nancy's). Two of them have been mentioned above: No man's land, The band played Waltzing Mathilda. The third and least known of them is 'For king and for country'.

For King and for Country
we fought and we died
in the first flush of dawn
at the fields of the Somme.

Wolfgang