<P> Kendrick Clements claims bureaucratic decision - making was one of the main sources pushing the United States to declaring war on Germany and aligning itself with the Allies . He cites the State Department's demand that Germany's submarines obey outdated, 18th century sailing laws as one of the first missteps by the United States bureaucracy regarding the war . By doing so, the United States had essentially given Germany the choice of whether or not the U.S. would enter the war . Secretary of State William Jennings Bryan spent most of the fall of 1914 out of contact with the State Department, leaving the more conservative Robert Lansing with the ability to shape American foreign policy at the time . One of these decisions was made in response to British protests that the Germans were using U.S. radio towers to send messages to their warships . Immediately prior to the war starting in 1914, Britain had cut all cable communications leading out of Germany, including the trans - Atlantic cable . The US Government permitted German embassies to use the US cable lines for "proper" diplomatic business . Germany argued that usage of the towers was necessary to allow efficient contact between the U.S. and Germany . Lansing responded by requiring both sides to give the U.S. Navy copies of the messages they sent over the towers . The French and British were still able to use the cables, forcing Germany to be the only belligerent required to provide the U.S. with their messages . This and other seemingly small decisions made by Lansing during this time would eventually stack up, shifting American support towards the Allies . </P> <P> Once Germany had decided on unrestricted submarine warfare in January 1917, and knowing it would be attacking all American ships in the North Atlantic, it tried to line up new allies, especially Mexico . Arthur Zimmermann, the German foreign minister, sent the Zimmermann Telegram to Mexico on January 16, 1917 . Zimmerman invited Mexico (knowing their resentment towards America since the 1848 Mexican Cession) to join in a war against the United States . Germany promised to pay for Mexico's costs and to help it recover the territory annexed by the U.S. in 1848 . These territories included the present day states of California, Nevada, Utah, most of Arizona, about half of New Mexico and a quarter of Colorado . British intelligence intercepted and decoded the telegram and passed it to the Wilson administration . The White House would release it to the press on March 1st . Anger grew further as the Germans began sinking American ships, even as isolationists in the Senate launched a filibuster to block legislation for arming American merchant ships to defend themselves . </P> <P> In early 1917 Berlin forced the issue . Its declared decision on 31 January 1917 to target neutral shipping in a designated war - zone became the immediate cause of the entry of the United States into the war . Five American merchant ships went down in March . Outraged public opinion now overwhelmingly supported Wilson when he asked Congress for a declaration of war on April 2, 1917 . </P> <P> Historians such as Ernest R. May have approached the process of American entry into the war as a study in how public opinion changed radically in three years' time . In 1914 most Americans called for neutrality, seeing the war a dreadful mistake and were determined to stay out . By 1917 the same public felt just as strongly that going to war was both necessary and wise . Military leaders had little to say during this debate, and military considerations were seldom raised . The decisive questions dealt with morality and visions of the future . The prevailing attitude was that America possessed a superior moral position as the only great nation devoted to the principles of freedom and democracy . By staying aloof from the squabbles of reactionary empires, it could preserve those ideals--sooner or later the rest of the world would come to appreciate and adopt them . In 1917 this very long - run program faced the severe danger that in the short run powerful forces adverse to democracy and freedom would triumph . Strong support for moralism came from religious leaders, women (led by Jane Addams), and from public figures like long - time Democratic leader William Jennings Bryan, the Secretary of State from 1913 to 1916 . The most important moralist of all was President Woodrow Wilson--the man who dominated decision making so totally that the war has been labelled, from an American perspective, "Wilson's War". </P>

What formed american opinion at the beginning of world war i