This theme is concerned with the representation of warfare in all its forms, with a primary focus on posters, artwork and music. Many posters which have not been assigned to other themes appear here. There are posters from World War I issued in Canada, the United States, Belgium, France and Germany. Posters from World War II are also included; twelve of them made up a 2008 calendar issued by McMaster University Library; those selected were issued by Canada, the United States, Britain and Australia. Posters concern recruitment (there is a case study on British recruiting posters in World War I), the purchase of victory bonds and war savings certificates, home management and other topics. There is also a series of posters concerning the occupation of Germany at the end of World War I. Two case studies of Hamilton, Ontario during the World Wars contain posters and other materials included in the theme The Hamilton Connection.

Also included in this theme is artwork from the First World War. It includes depictions of landscapes, ships, guns, tanks, bridges, bomb damage. “The Wounded Soldier” despite its title is a delightful water-colour. Additional artwork from World War I can be found under the theme The Soldier Artist and Poet. Also collected in this theme is a decorative grouping of souvenir commemorations from World War I printed by S. Burgess.