Illustration showing a soldier's foot with gangrene caused by vascular thrombosis from chlorine poisoning during the First World War. Chlorine gas was first used as a killing agent in the war by German forces in April 1915. The use of chemical weapons in the First World War is believed to have resulted in the deaths of 90,000 soldiers and more than 1.3 million casualties. This illustration was published in An Atlas of Gas Poisoning, 1918 by the American Red Cross. It was made as a guide for inexperienced officers in the American Expeditionary Force the characteristic injuries of different types of poisoning.