Of couse what's appropriate may depend on the nature of the project and how authentic you want it to be . . WWI pieces are hardly appropriate to something about your civil war!

For a tune I'd suggest "Battle of the Somme" - which is said to be a folk composition from the trenches at that time, and works well as a march/processional. Well, we used it as such for an Hiroshima Day commemoration at Sidmouth one year.

George