Taken as an extract from Valiant Hearts: The Great War Walkthrough
For most people, this may be a difficult trophy, but not an impossible one. At time of writing the walkthrough (long after the initial rush), ten percent of the people who have completed this level have also earnt this trophy. You could take that as high or low depending on how you look at it.
This trophy is the meat and bones of Chapter 4 Part 5: Saint Mihiel. If you haven’t made it that far you should stop reading.
In fact, if you haven’t completed the story yet, I would suggest you do that first before worrying about this trophy. If you mess up just keep going, try and keep him alive. Finish the fight. I’ll be waiting here with your trophy when you’re ready to roll up your sleeves and sweat for it.
Indeed, you can replay this part directly from chapter select so you will not really waste any time having to backtrack to it (like some of the Collectibles late into their Parts).