The most famous image of World War I is from a recruiting poster. "BRITONS," the poster blares across its top Admiral Kitchener--the most decorated and admired figure in the British military at the time--stares out with a steely glance, broad moustaches flaring from his face, finger thrust insistently at the spellbound viewer. Alongside his powerful, resolute face are the words "Wants You." The message was clear, and impossible to ignore: this war...