You would need this tool to help you build trenches. You could also use this to protect yourself from rats if you don't have anything else.
This will help you to not breath in the toxic fumes. They would be used on civilian populations. if the gas is inhaled their lungs would burst and the soldiers would die.
Field Emergency Kit
If people get hurt or sick out on the field this could help save someones life. You could use the alcohol to kill bacteria so it wont grow an infection.
Helmets can help protect soldiers head from getting any severe damage. If someone gets hit in the head with a shovel then they will be protected by the helmet.
You would need this for protection to bring down your enemies. Sense nothing else was invented back then these guns can be used to shoot far away and it was your only protection.