Taut with the urgent energy of wartime mobilisation, this American linen-era military training card shows two soldiers — one a British-style officer with peaked cap pointing downrange, the other a U.S. doughboy in campaign hat — lying prone behind a tripod-mounted machine gun on an open training ground, the wide prairie sky stretching behind them. Captioned "Birdmen Training With Machine Guns," the card is part of the "Series 595 Army Training — 12 designs" set published by U.B.D. (United Book and Document Co., or a related American publisher), with the copyright code 6922 visible in the lower left. The term "Birdmen" — aviators — combined with machine-gun ground training reflects the emerging doctrine of World War One aerial gunnery, where pilots and observers drilled on ground-mounted weapons to build instinctive aim before graduating to airborne observers' rings. The mixed uniforms visible — one figure appearing in British-pattern khaki with peaked cap, the other in the characteristic Montana-peak campaign hat of the AEF — suggest this may document joint Allied training in the United States or Canada circa 1917–18, making it a vivid document of the citizen-soldier moment that defined the Great War's final phase.