This is a First World War gas mask for a horse. The role of horses in warfare changed significantly during the First World War as changes in technology made cavalry vulnerable and horses began to be replaced by tanks at the front line. Nevertheless, the gas mask demonstrates the continued importance of horses behind the front lines as the military invested in protection for them in the face of another technological change, the use of gas. The object can be used to discuss these changes and to prompt examination of the experience of warfare at the front.