Trench warfare
Soldiers fighting in World War I lived in trenches and fought from far distances. They were faced with horrible conditions and were exposed to many sicknesses. Rats who fed themselves on human remains infested the trenches. Lice were also a huge problem causing the soldiers to itch continuously. Slugs and horned beetles crowded the side of the trenches. Many soldiers got "Trench foot", a fungal infection of the feet caused by unsanitary trench conditions. It could result in amputations. Lastly, rotting corpses laid around in the trenches, resulting in horrible smells.