How the Decision to Declare War was Influenced The decision to declare war on Germany was greatly influenced by allied propaganda, American economic interests, and German naval policies. Although most Americans were against involvement in a European war these influences increased its position in the war. The loss of money and the demand for defense was necessary for the war. Also propaganda was running high at this time. Before World War I broke out, European countries had begun to increase and bulk up their military forces. In the late 1800’s it was known that Germany had the best army in the world. These m