From the first moments of the war, the involved nations published their own accounts of the causes of the conflict and the particulars of the battles. The First World War was the first in which mass media played a significant part in sending news from the front to the folks back home. It was also the first war to systematically produce government propaganda aimed at the general public. All involved were compelled to recognize that they had to justify the righteousness of the war and, to this end, themes such as patriotism and nationalism played an important role. It was also crucial to all belligerents that they be perceived to be acting purely in self-defense.
The armies of continental Europe were made up of conscripts, who had little choice about going to war. In 1914 the British Army, by contrast, was made up of professionals and then volunteers. The British needed propaganda to justify the war to the people, to help promote recruitment into the armed forces, and to convince the population that their sacrifices would be rewarded. One of the most enduring images of the war remains the distinctive recruitment poster of Lord Kitchener's mustachioed face and intimidating finger imploring the British population that "Your Country Needs YOU."
So successful was the Kitchener image that it was the basis of an American equivalent. Originally published as the cover for the July 6, 1916, issue of Leslie's Weekly with the title "What Are You Doing for Preparedness?" this portrait of "Uncle Sam" went on to become — according to its creator, James Montgomery Flagg — "the most famous poster in the world." Over four million copies were printed between 1917 and 1918, as the United States entered World War I and began sending troops and matériel into war zones.