Between 1914 and 1918, there were 15 million deaths, military and civilian. Terrifying balance of the first modern conflict in history, in which new weapons were used before their destructive power was known, and equipment was enhanced from the difficulties faced on the front. This is how grenades that failed to fall into mud puddles were perfected. Or that the submachine guns replaced the previous models, which weighed up to sixty pounds and required up to six men in their operation.