First I drew a lot of tiny details--soldiers, buildings, etc.--in pencil, as well as the lay of the land and the window which frames the scene. Then I used the pastel crayons and reheightened some of the pencil work.
Inspired by something a buddy and I used to do in 3rd grade while sitting quietly in the auditorium at L.O. Donald Elementary during Auditorium Class. First pencil; then fine-tip marker; then a bit of pastel crayon.