He was killed in action at Villers-Bretonneux in the Somme in June 1918, shortly after the Australians saved the village from the Germans.

More than any other letters, those by the former carpenter to his wife encapsulate the longing, fears and insecurities felt by many soldiers during World War I, says Rebecca Britt, acting head of military heraldry and technology at the Australian War Memorial in Canberra, and author of Stories of Love and War.

''Marie mine, I want to get back to you again. I want so much to have you in my arms, making love to you and cuddling you close to me,'' McFarlane wrote from France in June 1917. ''When will that come again, Girlie? If I had ever thought I would be so long away from my own Wifie, I would never have enlisted. This is not life to me, being away from you.''

The letters by McFarlane are such eloquent expressions of love and longing that the reader feels both envious of Marie as the recipient of such outpourings and slightly voyeuristic.

''Even from the beginning he was wondering what had he done, why had he left her. The refrain going through them was how much he longed to be back with her, creating a family, living their lives together. He almost made it through the war, but he was one of those thousands of Australians who never made it back to form a family.''

Within months of signing up in January 1916, McFarlane was regretting his decision. By 1917, he was even hoping to be wounded. ''I am not contented and never will be until I am with you. The only way seems to [be to] get a wound that would take me back to Australia,'' he wrote from Fovant, a camp in Wiltshire, England, that housed soldiers destined for France.

Many intimate parts of McFarlane's more passionate imaginings of cuddling Marie were cut before the letters were donated to the war memorial. ''Girlie, I am getting fed up over here,'' he wrote from France to Marie on April 29, 1917, remembering the last weekend they had spent together a year earlier.

''I want to write you Wife of how much I want you, of how much I love you and I can't seem to be able to put my thoughts to paper … I want to be lying beside you, where we used to go on Sunday afternoons behind that big rock on the beach. I want to be lying there with you Marie Mine, loving and kissing you … I want to look into your eyes Girlie, to let my hands roam about your arms and your hair and then at night when you would let me take … [rest of letter missing].''

After the war, many families cut the more private parts of letters, never imagining that they would be of interest to the memorial. Britt says many people regarded letters such as these as ''just mum and dad's romance'' but that's not true.

''Wars are fought by people, they're fought by ordinary men and women who are going off and sacrificing for their country. These letters really do show us that. It could be our mums and dads, it could be us in another age, and these letters really do bring home the effects of war and the impact of war on our society as well as on individual families.''

McFarlane's love for Marie was returned. The young widow grieved so much for her husband that she agonised for years over what to put on his gravestone at Villers-Bretonneux. Finally, she decided on ''Jesus my god and my all, I give to you, Peter, my husband''. Six years later she said the heartache was still deep and painful, and ''these words always help me bear my loss''.

McFarlane is buried in one of 1089 graves at Villers-Bretonneux, which also contains the remains of thousands of unknown Australians.