United States was drawn into World War I in April 1917. Although President Wilson made efforts to keep the country out of war, there were many factors that resulted in the American entry, such as:
the basic urge to support for the British and reluctance to support the Germans;
the atrocities that took place in Belgium in 1914;
the sinking of the <em>RMS Lusitania</em> in 1915, that carried peaceful Americans;
the political upheaval of Russia;
the weakening of Britain and France;
the German resolution not no warn passengers or crews before attacking them;