It's the ever present question: What if...? What if they had met at the front? What if they had both survived? What if Owen could have told Todd he loved him? Questions, which can never be answered, which makes them powerful, so powerful they can destroy a life.
When I visited Verdun and I saw all those white crosses, I practically felt the lost chances, the unanswered questions, the destroyed hope, the ruined lifes that rested there and elsewhere. You tied all this to a gripping story, made it even more clear, showed what sacrifices have been made.