Korean War US 5 Gallon Collapsible Water Bladder Carrying Bag Trench Art WW2

I think this is either WW2 or Korean War era. I believe the person who owned this had their reasoning behind the custom alterations. Please let me know if I mislabeled anything. Canteen bladder not present or included. The bag is cut at an angle on both sides at the bottom and cut at the top.