A mercy dog (also known as an ambulance dog, Red Cross dog, or casualty dog) was a dog that served in a paramedical role in the military, most notably during World War I. They were often sent out after large battles, where they would seek out wounded soldiers, and they were well-suited to the conditions of trench warfare. They carried first-aid supplies that could then be used by wounded soldiers, and comforted dying soldiers who were mortally wounded. They were also trained to guide combat medics to soldiers who required extensive care. Many mercy dogs were trained by national Red Cross societies to serve the country in which the specific society operated. The German army called such dogs medical dogs. As many as 20,000 dogs are estimated to have served as mercy dogs in World War I and World War II, and they have been credited with saving thousands of lives. Such dogs were also used by the United States in the Korean War.