the character of Sergeant Dunne seems to have been inspired (at least in part) by the real-life British war poet Siegfried Sassoon, by way of Pat Barker's novel Regeneration.
The primary inspiration was Gross's grandfather, who served in the war; whether he nailed a hot nurse by the light of mortar-fire is indeterminate.
As to Hong Kong, most people aren't even aware of Canadian participation in the Pacific Theatre, because there wasn't much of it. My grandfather was on the Uganda
, actually (he was incredibly pissed off that the ship voted to go home; he blamed the French).