The war also saw a lot of civilians die, especially in the Ottoman Empire, where more than 2 million of the 3 million people killed were non-combatants. But like so many other wars, World War I's most efficient killer was disease. Stupid disease, always hijacking history. Dysentery, typhus, and cholera were rampant, and otherwise minor injuries would prove fatal when gangrene set in. I mean, 25% of arm wounds among German soldiers were fatal. And that's not even to mention the famous influenza epidemic that broke out toward the end of the war, which killed more than three times as many people as the war itself. The main reason the war was so deadly was the combination of new technology and outdated tactics.