Military book

I know this is a long shot but I thought I'd try.

My grandpa passed in January and he wanted me to read a book he loved, he said that the part about bmq was exactly like when he was in the war. When I was visiting him in the hospital I had started reading it to him, but when he passed everything was a blur and I just realized we must have left it there. I called the hospital and the nurses are trying to see if they can find but I thought I'd ask here to.

So this is all I know: It was a mass market paperback, I think the cover had a picture of a few military guys on it? It was probably published 80s-90s, and it was about the Australian military and I think during the Korean of Vietnam war. It starts off with a character (I think named Jack? Or a name like that) as he starts bmq. I got as far as chapter two, but if I read it I know I'd recognize it.

If I remember any other details I'll add to this post, thank you in advance for any help