Hey Guys & Gals!
This is my 100% Achievement/Trophy Guide walkthrough (& All Collectibles) for 11-11 Memories Retold and is divided into 2 parts.
So this happens in Part 2 - Chapter 5, and as Harry you start off in the area wading through muk and water.
The area, although quite big, really only opens to one sort of path.
Keep following the right hand side until you get to a few soldiers next to a table and they tell you where Major Barret is.
From this point, keep heading right and then straight until you see a few soldiers next to a tent with Gas masks on. Next to them is gas bottles that are on. Just press
next to them to unlock it.
If you prefer a video guide, skip to 2:26:20 in my Part 1 video.