Trenches during WWI were unsanitary places that exposed soldiers to rats, lice, trench foot, and shell shock. New weapons in 1914 like machine guns, airplanes, and tanks were developed, but commanders failed to understand how to effectively use this new technology. As a result, battles involved attrition strategies that led to massive casualties. Poison gases, larger artillery, tanks, planes, and submarines increasingly inflicted death on a larger scale and changed the nature of warfare.