Entrenching Tool
An entrenching tool would be very helpful to have. This could save your life and others to. By having this tool it allows you to get your body out of harms way.
Rifle
A rifle will protect you. If you don't have a rifle you will most likely die. This will save you many times.
Medical Kit
A medical kit will be very useful. In war you will encounter all types of injuries. With this you will be able to help you and other people who are hurt. You could possibly buy yourself some time too.
Gas Mask
They will use poison gas in war. A gas mask will keep all the chemicals out. If you didn't have this on you would die because of all the chemicals that you are breathing in.
A Vaccination
A vaccination is very helpful. This may not sound like a big deal but it is. Without a vaccination you will be open to all kinds of diseases. if you get a vaccination you have less of a chance of getting one.
Citations
WW1 Trench Warfare Btb.jo Creative Commons Attribution-Share Alike 4.0 International