<P> American foreign policy was largely determined by President Woodrow Wilson , who had shown little interest in foreign affairs before entering the White House in 1913 . His chief advisor was `` Colonel '' Edward House , who was sent on many top - level missions . With the outbreak of war in 1914 , the United States declared neutrality and worked to broker a peace . It insisted on its neutral rights , which included allowing private corporations and banks to sell or loan money to either side . With the British blockade , there were almost no sales or loans to Germany , only to the Allies . The widely publicized German atrocities in Germany Shocked American public opinion . Neutrality was supported by Irish - Americans , who hated Britain , by German Americans who wanted to remain neutral , and by women and the churches . It was supported by the more educated upscale WASP element , led by Theodore Roosevelt . Wilson insisted on neutrality , denouncing both British and German violations , especially those German violations in which American civilians were killed . The German U-boat torpedoed the RMS Lusitania in 1915 . It sank in 20 minutes , killing killed 128 American civilians and over 1000 Britons . It was against the laws of war to sink any passenger ship without allowing the passengers to reach the life boats . American opinion turned strongly against Germany as a bloodthirsty threat to civilization . Germany apologized and repeatedly promised to stop attacks by its U-boats , but reversed course in early 1917 when it saw the opportunity to strangle Britain by unrestricted submarine warfare . It also made overtures to Mexico , in the Zimmermann Telegram , hoping to divert American military attention to south of the border . The German decision was not made or approved by the civilian government in Berlin , the by the military commanders and the Kaiser . They realized it meant war with the United States , but hoped to weaken the British by cutting off its imports , and strike a winning below with German soldiers transferred from the Eastern front , where Russia had surrendered . Following the repeated sinking of American merchant ships in early 1917 , Wilson asked and obtained a declaration of war in April 1917 . He neutralized the antiwar element by arguing this was a war With the main goal of ending aggressive militarism and indeed ending all wars . During the war the U.S. was not officially tied to the Allies by treaty , but military cooperation meant that the American contribution became significant in mid-1918 . After the failure of the German spring offensive , as fresh American troops arrived in France at 10,000 a day , the Germans were in a hopeless position , and surrendered . Coupled with Wilson 's Fourteen Points in January 1918 , the U.S. now had the initiative on the military , diplomatic and public relations fronts . Wilsonianism -- Wilson 's ideals -- had become the hope of the world , including the civilian population Germany itself . </P>
what was the united states foreign policy after ww1 started
neutrality