Complex sentence: The song is a vivid account of the memories of a young Australian man who, in 1915, had been recruited into the ANZACs and sent to Gallipoli--who "for ten weary weeks" kept himself alive as "around me the corpses piled higher".
Split into simpler sentences: The song is a vivid account of the memories of a young Australian man who, in 1915, had been recruited into the ANZACs and sent to Gallipoli. For "ten weary weeks" he kept himself alive as "around me the corpses piled higher".