During the First World War the North American Navy was very small compared to the armies mobilized by the European armies. With the declaration of war of the USA to Germany in April of 1917, the Congress approved an Act creating the Selective Service System. This law gave the president - W. Wilson at that time - the power of conscription, calling men for military service. The system consisted of a classification of five levels and expanded the previously allowed ages. By the end of the recluting days, it had achieved more than two million volunteers. This conscription campaign was very successful because it was accompanied by a strong publicity that encouraged men to a patriotic attitude, which guaranteed a high success rate. This recruitment system was left without effect in 1920.
