American entry into World War I The United States ' entry into World War I came in April 1917 , after two and a half years of efforts by President Woodrow Wilson to keep the United States neutral . Americans had no idea that war was imminent in Europe in the summer of 1914 , and tens of thousands of tourists were caught by surprise . The U . S . government , under Wilson ' s firm control , called for neutrality " in thought and deed " . Apart from an Anglophile element supporting the British , American public opinion went along with neutrality at first . The sentiment for neutrality was strong among Irish Americans , German Americans and Swedish Americans , as well as among church leaders and women . However , the citizenry increasingly came to see the German Empire as the villain after news of atrocities in Belgium in 1914 , and the sinking of the passenger liner " RMS Lusitania " in 1915 in defiance of international law . Wilson made all the key decisions and kept the economy on a peacetime basis , while allowing large - scale loans to the United Kingdom and France . To preclude making any military threat Wilson made no preparations for war and kept the army on its small peacetime basis despite increasing demands for preparedness . At the beginning of 1917 Germany decided to resume on all commercial ships headed toward Britain , realizing that this decision would almost certainly mean war with the United States . Germany also offered a military alliance to Mexico , as intercepted and decoded by the British in the Zimmerman Telegram , and publication of that offer outraged Americans just as German U - boats ( submarines ) started sinking American ships in the North Atlantic . Wilson asked Congress for " a war to end all wars " that would " make the world safe for democracy " , and Congress voted to declare war on April 6 , 1917 . Submarines and Blockades . A critical indirect strategy used by both sides was the blockade . The British Royal Navy successfully stopped the shipment of most war supplies and food to Germany . Neutral American ships that tried to trade with Germany were seized or turned back . The strangulation came about very slowly , because Germany and the Central Powers ( its allies ) controlled extensive farmlands and raw materials . However , it was eventually successful because Germany and Austria - Hungary had taken so many farmers into their armies . By 1918 , German cities were on the verge of starvation ; the front - line soldiers were on short rations and were running out of essential supplies . Germany also considered a blockade . " England wants to starve us " , said Admiral Alfred von Tirpitz , the man who built the German fleet and who remained a key advisor to the Kaiser Wilhelm II . " We can play the same game . We can bottle her up and destroy every ship that endeavors to break the blockade " . Unable to challenge the more powerful Royal Navy on the surface , Tirpitz wanted to scare off merchant and passenger ships en route to Britain . He reasoned that since the island of Britain depended on imports of food , raw materials , and manufactured goods , scaring off a substantial number of the ships would effectively undercut its long - term ability to maintain an army on the Western Front . While Germany had only nine long - range U - boat s at the start of the war , it had ample shipyard capacity to build the hundreds needed . However , the United States demanded that Germany respect international law , which protected neutral American ships on the high seas from seizure or sinking by either belligerent . Furthermore , Americans insisted that the drowning of innocent civilians was barbaric and grounds for a declaration of war . The British frequently violated America ' s neutral rights by seizing ships . Wilson ' s top advisor , Colonel Edward M . House commented that , " The British have gone as far as they possibly could in violating neutral rights , though they have done it in the most courteous way " . When Wilson protested British violations of American neutrality , the British backed down . German submarines , however , torpedoed ships without warning , and some sailors and passengers drowned . Berlin explained that submarines were so vulnerable that they dared not surface near merchant ships that might be carrying guns and which were too small to rescue submarine crews . Britain armed most of its merchant ships with medium calibre guns that could sink a submarine , making above - water attacks too risky . In February 1915 , the United States warned Germany about misuse of submarines ; but on May 7 , Germany torpedoed the British passenger liner " RMS Lusitania " , sinking her . This act of aggression caused the loss of 1 , 198 civilian lives , including 128 Americans . The sinking of a large , unarmed passenger ship , combined with the previous atrocity stories from Belgium , shocked Americans and turned public opinion hostile to Germany , although not yet to the point of war . Wilson issued a warning to Germany that it would face " strict accountability " if it sank more neutral U . S . passenger ships . < ref name = http : / / www . firstworldwar . com / wilsonwarning > < / ref > Berlin acquiesced , ordering its submarines to avoid passenger ships . By January 1917 , however , Field Marshal Paul von Hindenburg and General Erich Ludendorff decided that an unrestricted submarine blockade was the only way to break the stalemate on the Western Front . They demanded that Kaiser Wilhelm order unrestricted submarine warfare be resumed . Germany knew this decision meant war with the United States , but they gambled that they could win before America ' s potential strength could be mobilized . However , they overestimated how many ships they could sink and thus the extent Britain would be weakened . Finally , they did not foresee that convoys could and would be used to defeat their efforts . They believed that the United States was so weak militarily that it could not be a factor on the Western Front for more than a year – a mistake that would ultimately prove to be fatal to the German Empire . The civilian government in Berlin objected , but the Kaiser sided with his military . Elites . National elites split into three distinct groups . First were the anti - war people ( " pacifists " loosely defined ) , who wanted to keep America out at all costs , and rejected as equally immoral the British and German Empires . The leaders included Secretary of State William Jennings Bryan ( a three - time Democratic nominee for president ) , Republican Senator Robert M . La Follette , Sr . , woman ' s leader Jane Addams ( a Progressive ) and industrialist Henry Ford ( a Democrat ) . Secondly , the " liberal internationalists " reluctantly supported armed force to create a collective security system . They included President Woodrow Wilson and former president William Howard Taft . Finally , the " Atlanticists " sought a security relationship with Britain ; they were led by former President Theodore Roosevelt , Major General Leonard Wood , and Republican Senators Elihu Root and Henry Cabot Lodge . Business considerations . The beginning of World War I in Europe coincided with the end of the Recession of 1913 – 1914 in America . Exports to belligerent nations rose rapidly over the first four years of the War from $ 824 . 8 million in 1913 to $ 2 . 25 billion in 1917 . Loans from American financial institutions to the Allied nations in Europe also increased dramatically over the same period . Economic activity towards the end of this period boomed as government resources aided the production of the private sector . Between 1914 and 1917 , industrial production increased 32 % and GNP increased by almost 20 % . The improvements to industrial production in the United States outlasted the war . The capital build - up that had allowed American companies to supply belligerents and the American army resulted in a greater long - run rate of production even after the war had ended in 1917 . In 1913 , J . P . Morgan , Jr . took over the House of Morgan , an American - based investment bank consisting of separate banking operations in New York , London , and Paris , after the death of his father , J . Pierpont Morgan . The House of Morgan offered assistance in the wartime financing of England and France from the earliest stages of the war in 1914 through America ’ s entrance in 1917 . J . P . Morgan & Co . , the House of Morgan ’ s bank in New York , was designated as the primary financial agent to the British government in 1914 . The same bank would later take a similar role in France and would offer extensive financial assistance to both warring nations . J . P . Morgan & Co . became the primary issuer of loans to the French government by raising money from American investors . Morgan , Harjes , the House of Morgan ’ s French affiliated bank , controlled the majority of the wartime financial dealings between the House of Morgan and the French government after primary issuances of debt in American markets . Relations between the House of Morgan and the French government became tense as the War raged on with no end in sight . France ’ s ability to borrow from other sources diminished , leading to greater lending rates and a depressing of the value of the Franc . After the War , in 1918 , J . P . Morgan & Co . continued to aid the French government financially through monetary stabilization and debt relief . Because America was still a declared neutral state , the financial dealings of American banks in Europe caused a great deal of contention between Wall Street and the U . S . government . William Jennings Bryan , the Secretary of State at the time , strictly opposed financial support of warring nations and officially banned loans to the belligerents in August 1914 . In a letter to President Wilson dated August 10 , 1914 , Secretary Bryan recognized that “ refusal to loan to any belligerent would natural tend to hasten a conclusion of the war ” J . P . Morgan managed to avoid the ban and issued loans to France including one in March 1915 and another in October 1915 , the latter amounting to US $ 500 , 000 , 000 . Although the stance of the U . S . government was that ending such aid could hasten the end of the war and save millions of lives , little else was done to insure the adherence to the ban on loans . The American steel industry had faced difficulties and declining profits during the Recession of 1913 – 1914 . As war began in Europe , however , the increased demand for tools of war began a period of heightened productivity that alleviated many U . S . industrial companies from the low - growth environment of the recession . Bethlehem Steel took particular advantage of the increased demand for armaments abroad . Prior to American entrance into the War , these companies benefitted from unrestricted commerce with sovereign customers abroad . After President Wilson issued his declaration of war , the companies were subjected to price controls created by the U . S . Trade Commission in order to insure that the U . S . military would have access to the necessary armaments . By the end of the War in 1918 , Bethlehem Steel had produced 65 , 000 pounds of forged military products and 70 million pounds of armor plate , 1 . 1 billion pounds of steel for shells , and 20 . 1 million rounds of artillery ammunition for Britain and France . Bethlehem Steel took advantage of the domestic armaments market and produced 60 % of the American weaponry and 40 % of the artillery shells used in the War . Even with price controls and a lower profit margin on manufactured goods , the profits resulting from wartime sales expanded the company into the third largest manufacturing company in the country . Bethlehem Steel became the primary arms supplier for the United States and other allied powers again in 1939 . Public opinion . A cosmopolitan group of upper and upper - middle class businessmen based in the largest cities took the lead in promoting military preparedness and in defining how far America could be pushed around before it would fight back . Many public figures hated war — Secretary of State William Jennings Bryan was the most prominent , and he resigned when he thought Wilson had become too bellicose . Grassroots opposition to American entry came especially from German and Irish elements . Parties . A surprising factor in the development of American public opinion was how little the political parties became involved . Wilson and the Democrats in 1916 campaigned on the slogan " He kept us out of war ! " , saying a Republican victory would mean war with both Mexico and Germany . His position probably was critical in winning the Western states . Charles Evans Hughes , the GOP candidate , insisted on downplaying the war issue . The Socialist party talked peace . It won 2 % of the 1916 vote for Eugene V . Debs , blamed the war on capitalism and pledged total opposition . " A bayonet " , its propaganda said , " was a weapon with a worker at each end " . When war began however , about half the Socialists , typified by Congressman Meyer London , supported the decision ; the rest , led by Debs , remained ideological and die - hard opponents . Workers , farmers , and African Americans . The working class was relatively quiet , and tended to divide along ethnic lines . Samuel Gompers , head of the AFL , denounced the war in 1914 as " unnatural , unjustified , and unholy " , but by 1916 he was supporting Wilson ' s limited preparedness program , against the objections of Socialist union activists . In 1916 the labor unions supported Wilson on domestic issues and ignored the war question . The war at first disrupted the cotton market ; Britain blockaded shipments to Germany , and prices fell from 11 cents a pound to only 4 cents . By 1916 , however , the British decided to bolster the price to 10 cents to avoid losing Southern support . The cotton growers seem to have moved from neutrality to intervention at about the same pace as the rest of the nation . Midwestern farmers generally opposed the war , especially those of German and Scandinavian descent . The Midwest became the stronghold of isolationism ; other remote rural areas also saw no need for war . The African - American community , which lived mostly in the pro - war South , did not take a strong position one way or the other . But once war began and black men were drafted , they worked to achieve equality . Old stock . Nationwide at all times the dominant voice was held by old - stock white Americans . The largest old - stock Protestant denominations ( Methodist , Baptist , Presbyterian , Disciples of Christ , Congregational , and some Lutheran groups ) loudly denounced the war at first : it was God ' s punishment for sin . Their moralism was aggressively focused on banishing evils ( like saloons ) from the face of the earth through Prohibition , and if they could be shown that German militarism was a similar evil , they would throw enormous weight . Wilson , the intensely religious son of a prominent theologian , knew exactly how to harness that moralism in his attacks on the " Huns " who threatened civilization , and his calls for an almost religious crusade on behalf of peace . Anglophiles . Upwards of four - fifths of America ' s social , political , and economic leaders were of English or Scottish descent ( usually Episcopalian , Baptist , Methodist or Presbyterian ) . Apart from clergymen , most wanted Britain to win , though at first not to the point of American entry . Magazine editors , newspaper reporters , book publishers , college professors , intellectuals , artists , and writers were overwhelmingly pro - British . German Americans . German Americans by this time usually had only weak ties to Germany ; however , they were fearful of negative treatment they might receive if the United States entered the war ( such mistreatment was already happening to German - descent citizens in Canada and Australia ) . Almost none called for intervening on Germany ' s side , instead calling for neutrality and speaking of the superiority of German culture . They were increasingly marginalized , however , and by 1917 had been excluded almost entirely from national discourse on the subject . Most Scandinavian - Americans also favored American neutrality . Churches and women . Leaders of most religious groups ( except the Episcopalians ) tended to pacifism , as did leaders of the woman ' s movement . A concerted effort was made by anti - war leaders , including Jane Addams , Oswald Garrison Villard , David Starr Jordan , Henry Ford , Lillian Wald , and Carrie Chapman Catt . Their goal was to convince Wilson to mediate an end of the war by bringing the belligerents to the conference table . Wilson indeed made an energetic , sustained and serious effort to do so , and kept his administration neutral , but he was repeatedly rebuffed by Britain and Germany . Finally in 1917 Wilson convinced some of them that to be truly anti - war they needed to support what Wilson promised would be " a war to end all wars " . Once war was declared , the more liberal denominations , which had endorsed the Social Gospel , called for a war for righteousness that would help uplift all mankind . The theme — an aspect of American exceptionalism — was that God had chosen America as his tool to bring redemption to the world . American bishops of the Roman Catholic Church maintained a general silence toward the issue of intervention . Millions of Catholics lived in both warring camps , and Catholic Americans tended to split on ethnic lines in their opinions toward American involvement in the war . At the time , heavily Catholic towns and cities in the East and Midwest often contained multiple parishes , each serving a single ethnic group , such as Irish , German , Italian , Polish , or English . American Catholics of Irish and German descent opposed intervention most strongly . Pope Benedict XV made several attempts to negotiate a peace . All of his efforts were rebutted by both the Allies and the Germans , and throughout the war the Holy See maintained a policy of strict neutrality . Jewish American sympathies likewise broke along ethnic lines , though at the turn of the century , Germany and Austria were considered among the most tolerant of continental European countries , while the tsarist regime in Russia was notorious for its anti - Semitic policies . The Balfour Declaration of 1917 , in which the British government promised to help establish a Jewish homeland in Palestine , as well as Wilson ' s promise of self - determination , helped swing Jewish - Americans into the pro - Allied camp . Irish - Americans . The most effective domestic opponents of the war were Irish - American Catholics . They had little interest in the continent , but were adamant against helping the British Empire because it refused to allow independence for Ireland . The Easter Rising in Dublin in April 1916 was crushed within a week and its leaders executed by firing squad . Irish - Americans dominated the Democratic party in many large cities so Wilson had to take account of their views . They did not prevent him from being hostile to Germany , but they did force him to keep his distance from Britain . Indeed , Irish - American pressure influenced the United States into not accepting Britain ' s war aims as its own and define its own objectives , primarily self - determination . The Irish - American community thought they had Wilson ' s promise to promote Irish independence in exchange for their support of his war policies , but after the war they were bitterly disappointed by his refusal to support them in 1919 . Pro - Allied immigrants . Some British immigrants worked actively for intervention . London - born Samuel Insull , Chicago ' s leading industrialist , for example , enthusiastically provided money , propaganda , and means for volunteers to enter the British or Canadian armies . After the United States ' entry , Insull directed the Illinois State Council of Defense , with responsibility for organizing the state ' s mobilization . Immigrants from eastern Europe usually cared more about politics in their homeland than politics in the U . S . Spokesmen for Slavic immigrants hoped that an Allied victory would bring independence for their homelands . Large numbers of Hungarian immigrants who were liberal and nationalist in sentiment , and sought an independent Hungary , separate from the Austro - Hungarian Empire lobbied in favor of the war and allied themselves with the Atlanticist or Anglophile portion of the population . This community was largely pro - British and anti - German in sentiment . Albanian and Czech immigrants were enthusiastically pro - war and arguably pro - British . This brought them into line with the so - called " Anglophiles " or Pro - British Americans who themselves were primarily " old stock Americans " , whose ancestry went back to the original thirteen colonies and was primarily British in origin . Preparedness movement . By 1915 , Americans were paying much more attention to the war . The sinking of the " Lusitania " had a strong effect on public opinion because of the deaths of American civilians . That year , a strong " Preparedness " movement emerged . It argued that the United States needed to immediately build up strong naval and land forces for defensive purposes ; an unspoken assumption was that America would fight sooner or later . General Leonard Wood ( still on active duty after serving a term as Chief of Staff of the Army ) , former president Theodore Roosevelt , and former secretaries of war Elihu Root and Henry Stimson were the driving forces behind Preparedness , along with many of the nation ' s most prominent bankers , industrialists , lawyers and scions of prominent families . Indeed there emerged an " Atlanticist " foreign policy establishment , a group of influential Americans drawn primarily from upper - class lawyers , bankers , academics , and politicians of the Northeast , committed to a strand of Anglophile internationalism . Representative was Paul D . Cravath , one of New York ' s foremost corporation lawyers . For Cravath , in his mid - fifties when the war began , the conflict served as an epiphany , sparking an interest in international affairs that dominated his remaining career . Fiercely Anglophile , he strongly supported American intervention in the war and hoped that close Anglo - American cooperation would be the guiding principle of postwar international organization . The Preparedness movement had a " realistic " philosophy of world affairs — they believed that economic strength and military muscle were more decisive than idealistic crusades focused on causes like democracy and national self - determination . Emphasizing over and over the weak state of national defenses , they showed that America ' s 100 , 000 - man Army even augmented by the 112 , 000 National Guardsmen , was outnumbered 20 to one by Germany ' s army , which was drawn from a smaller population . Reform to them meant UMT or " universal military training " . They proposed a national service program under which the 600 , 000 men who turned 18 every year would be required to spend six months in military training , and afterwards be assigned to reserve units . The small regular army would primarily be a training agency . Antimilitarists complained the plan would make America resemble Germany ( which required two years ' active duty ) . Advocates retorted that military " service " was an essential duty of citizenship , and that without the commonality provided by such service the nation would splinter into antagonistic ethnic groups . One spokesman promised that UMT would become " a real melting pot , under which the fire is hot enough to fuse the elements into one common mass of Americanism " . Furthermore , they promised , the discipline and training would make for a better paid work force . The hostility to military service was so strong at the time it is difficult to imagine such a program winning approval ; indeed , even in World War II , when Stimson as Secretary of War proposed a similar program of universal peacetime service , he was defeated . Underscoring its commitment , the Preparedness movement set up and funded its own summer training camps at Plattsburgh , New York , and other sites , where 40 , 000 college alumni became physically fit , learned to march and shoot , and ultimately provided the cadre of a wartime officer corps . Suggestions by labor unions that talented working - class youth be invited to Plattsburgh were ignored . The Preparedness movement was distant not only from the working classes but also from the middle - class leadership of most of small - town America . It had had little use for the National Guard , which it saw as politicized , localistic , poorly armed , ill trained , too inclined to idealistic crusading ( as against Spain in 1898 ) , and too lacking in understanding of world affairs . The National Guard on the other hand was securely rooted in state and local politics , with representation from a very broad cross section of American society . The Guard was one of the nation ' s few institutions that ( in some northern states ) accepted blacks on an equal footing . The Democratic party saw the Preparedness movement as a threat . Roosevelt , Root and Wood were prospective Republican presidential candidates . More subtly , the Democrats were rooted in localism that appreciated the National Guard , and the voters were hostile to the rich and powerful in the first place . Working with the Democrats who controlled Congress , Wilson was able to sidetrack the Preparedness forces . Army and Navy leaders were forced to testify before Congress to the effect that the nation ' s military was in excellent shape . In fact neither the Army nor Navy was in shape for war . The Navy had fine ships but Wilson had been using them to threaten Mexico , and the fleet ' s readiness had suffered . The crews of the " Texas " and the " New York " , the two newest and largest battleships , had never fired a gun , and the morale of the sailors was low . The Army and Navy air forces were tiny in size . Despite the flood of new weapons systems unveiled in the war in Europe , the Army was paying scant attention . For example , it was making no studies of trench warfare , poison gas or tanks , and was unfamiliar with the rapid evolution of air tactics . The Democrats in Congress tried to cut the military budget in 1915 . The Preparedness movement effectively exploited the surge of outrage over the " Lusitania " in May 1915 , forcing the Democrats to promise some improvements to the military and naval forces . Wilson , less fearful of the Navy . embraced a long - term building program designed to make the fleet the equal of the Royal Navy by the mid - 1920s . " Realism " was at work here ; the admirals were Mahanians and they therefore wanted a surface fleet of heavy battleships second to none — that is , equal to Britain . The facts of submarine warfare ( which necessitated destroyers , not battleships ) and the possibilities of imminent war with Germany ( or with Britain , for that matter ) , were simply ignored . Wilson ' s program for the army touched off a firestorm . Secretary of War Lindley Garrison adopted many of the proposals of the Preparedness leaders , especially their emphasis on a large federal reserves and abandonment of the National Guard . Garrison ' s proposals not only outraged the localistic politicians of both parties , they also offended a strongly held belief shared by the liberal wing of the Progressive movement . They felt that warfare always had a hidden economic motivation . Specifically , they warned the chief warmongers were New York bankers ( like J . P . Morgan ) with millions at risk , profiteering munition makers ( like Bethlehem Steel , which made armor , and DuPont , which made powder ) and unspecified industrialists searching for global markets to control . Antiwar critics blasted them . These special interests were too powerful , especially , Senator LaFollette noted , in the conservative wing of the Republican Party . The only road to peace was disarmament , reiterated Bryan . Garrison ' s plan unleashed the fiercest battle in peacetime history over the relationship of military planning to national goals . In peacetime , War Department arsenals and Navy yards manufactured nearly all munitions that lacked civilian uses , including warships , artillery , naval guns , and shells . Items available on the civilian market , such as food , horses , saddles , wagons , and uniforms were always purchased from civilian contractors . Armor plate ( and after 1918 , airplanes ) were exceptions that have caused unremitting controversy for a century . After World War II , the arsenals and Navy yards were much less important than giant civilian aircraft and electronic firms , which became the second half of the " military - industrial complex " Peace leaders like Jane Addams of Hull House and David Starr Jordan of Stanford redoubled their efforts , and now turned their voices against the President because he was " sowing the seeds of militarism , raising up a military and naval caste " . Many ministers , professors , farm spokesmen and labor union leaders joined in , with powerful support from a band of four dozen southern Democrats in Congress who took control of the House Military Affairs Committee . Wilson , in deep trouble , took his cause to the people in a major speaking tour in early 1916 , a warmup for his reelection campaign that fall . Wilson seems to have won over the middle classes , but had little impact on the largely ethnic working classes and the deeply isolationist farmers . Congress still refused to budge , so Wilson replaced Garrison as Secretary of War with Newton Baker , the Democratic mayor of Cleveland and an outspoken opponent of preparedness . ( Garrison ' s kept quiet , but felt Wilson was " a man of high ideals but no principles " . ) The upshot was a compromise passed in May 1916 , as the war raged on and Berlin was debating whether America was so weak it could be ignored . The Army was to double in size to 11 , 300 officers and 208 , 000 men , with no reserves , and a National Guard that would be enlarged in five years to 440 , 000 men . Summer camps on the Plattsburg model were authorized for new officers , and the government was given $ 20 million to build a nitrate plant of its own . Preparedness supporters were downcast , the antiwar people were jubilant . America would now be too weak to go to war . Colonel Robert L . Bullard privately complained that " Both sides [ Britain and Germany ] treat us with scorn and contempt ; our fool , smug conceit of superiority has been exploded in our faces and deservedly . " The House gutted the naval plans as well , defeating a " big navy " plan by 189 to 183 , and scuttling the battleships . The battle of Jutland ( May 31 / June 1 , 1916 ) was used by the navalists to argue for the primacy of seapower ; they then took control in the Senate , broke the House coalition , and authorized a rapid three - year buildup of all classes of warships . A new weapons system , naval aviation , received $ 3 . 5 million , and the government was authorized to build its own armor - plate factory . The very weakness of American military power encouraged Berlin to start its unrestricted submarine attacks in 1917 . It knew this meant war with America , but it could discount the immediate risk because the U . S . Army was negligible and the new warships would not be at sea until 1919 by which time the war would be over , with Germany victorious . The notion that armaments led to war was turned on its head : refusal to arm in 1916 led to war in 1917 . Decision for war . By 1916 a new factor was emerging — a sense of national self - interest and nationalism . The unbelievable casualty figures were sobering — two vast battles caused over one million casualties each . Clearly this war would be a decisive episode in the history of the world . Every American effort to find a peaceful solution was frustrated . Henry Ford managed to make pacifism look ridiculous by sponsoring a private peace mission that accomplished nothing . German agents added a comic opera touch . The agent in charge of propaganda left his briefcase on the train , where an alert Secret Service agent snatched it up . Wilson let the newspapers publish the contents , which indicated a systematic effort by Berlin to subsidize friendly newspapers and block British purchases of war materials . Berlin ' s top espionage agent , debonnaire Franz Rintelen von Kleist was spending millions to finance sabotage in Canada , stir up trouble between the United States and Mexico and to incite labor strikes . The British were engaged in propaganda too , though not illegal espionage . But they did not get caught ; Germany took the blame as Americans grew ever more worried about the vulnerability of a free society to subversion . Indeed , one of the main fears Americans of all stations had in 1916 – 1919 was that spies and saboteurs were everywhere . This sentiment played a major role in arousing fear of Germany , and suspicions regarding everyone of German descent who could not " prove " 100 % loyalty . Americans felt an increasing need for a military that could command respect ; as one editor put it , " The best thing about a large army and a strong navy is that they make it so much easier to say just what we want to say in our diplomatic correspondence . " Berlin thus far had backed down and apologized when Washington was angry , thus boosting American self - confidence . America ' s rights and America ' s honor increasingly came into focus . The slogan " Peace " gave way to " Peace with Honor " . The Army remained unpopular , however . A recruiter in Indianapolis noted that , " The people here do not take the right attitude towards army life as a career , and if a man joins from here he often tries to go out on the quiet " . The Preparedness movement used its easy access to the mass media to demonstrate that the War Department had no plans , no equipment , little training , no reserves , a laughable National Guard , and a wholly inadequate organization for war . Motion pictures like " The Birth of a Nation " ( 1915 ) and " The Battle Cry of Peace " ( 1915 ) depicted invasions of the American homeland that demanded action . The press at the time reported that the only thing the military was ready for was an enemy fleet attempting to seize New York harbor — at a time when the German battle fleet was penned up by the Royal Navy . Navy Secretary Josephus Daniels , a journalist with pacifist leanings , had built up the educational resources of the Navy and made its War College in Newport an essential experience for would - be admirals . However , he alienated the officer corps with his moralistic reforms , including no wine in the officers ' mess , no hazing at Annapolis , and more chaplains and YMCAs . Ignoring the nation ' s strategic needs , and disdaining the advice of its experts , Daniels suspended meetings of the Joint Army and Navy Board for two years because it was giving unwelcome advice , chopped in half the General Board ' s recommendations for new ships , reduced the authority of officers in the Navy yards where ships were built and repaired , and ignored the administrative chaos in his department . Bradley Fiske , one the most innovative admirals in American naval history , in 1914 was Daniels ' top aide ; he recommended a reorganization that would prepare for war , but Daniels refused . Instead he replaced Fiske in 1915 and brought in for the new post of Chief of Naval Operations an unknown captain , William Benson . Chosen for his compliance , Benson proved a wily bureaucrat who was more interested in preparing for an eventual showdown with Britain than an immediate one with Germany . Benson told Sims he " would as soon fight the British as the Germans " . Proposals to send observers to Europe were blocked , leaving the Navy in the dark about the success of the German submarine campaign . Admiral William Sims charged after the war that in April 1917 , only ten percent of the Navy ' s warships were fully manned ; the rest lacked 43 % of their seamen . Light antisubmarine ships were few in number , as if Daniels had been unaware of the German submarine menace that had been the focus of foreign policy for two years . The Navy ' s only warfighting plan , the " Black Plan " assumed the Royal Navy did not exist and that German battleships were moving freely about the Atlantic and the Caribbean and threatening the Panama Canal . Daniels ' tenure would have been even less successful save for the energetic efforts of Assistant Secretary Franklin D . Roosevelt , who effectively ran the Department . In early 1917 Berlin forced the issue . The decision to try to sink every ship on the high seas was the immediate cause of American entry into the war . Five American merchant ships went down in March . If further evidence were needed , the German foreign minister , Arthur Zimmermann , approached Mexico for an alliance ; Mexico would join Germany in a war and be rewarded with the return of lost territories in Texas , New Mexico , and Arizona ( but not California ) . The Zimmermann Telegram was intercepted and decoded by British cryptographers . Outraged public opinion now overwhelmingly supported Wilson when he asked Congress for a declaration of war on April 2 , 1917 . The United States had a moral responsibility to enter the war , he proclaimed , to make the world safe for democracy . The future of the world was being determined on the battlefield , and American national interest demanded a voice . Wilson ' s definition of the situation won wide acclaim , and , indeed , has shaped America ' s role in world and military affairs ever since . Wilson saw that if Germany would win , the consequences would be bad for the United States . Germany would have dominated the continent and perhaps would gain control of the seas as well . Latin America could well have fallen under Berlin ' s control . The dream of spreading democracy , liberalism , and independence would have been shattered . On the other hand , if the Allies had won without help , there was a danger they would carve up the world without regard to American commercial interests . They were already planning to use government subsidies , tariff walls , and controlled markets to counter the competition posed by American businessmen . The solution was a third route , a " peace without victory " , according to Wilson . Public opinion , moralism , and national interest . 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 " Wilson ' s War " . In 1917 Wilson won the support of most of the moralists by proclaiming " a war to make the world safe for democracy . " If they truly believed in their ideals , he explained , now was the time to fight . The question then became whether Americans would fight for what they deeply believed in , and the answer turned out to be a resounding " Yes " . Antiwar activists at the time and in the 1930s , alleged that beneath the veneer of moralism and idealism there surely must have been some sordid forces at work . Some suggested a conspiracy on the part of New York City bankers holding $ 3 billion of war loans to the Allies , or steel and chemical firms selling munitions to the Allies . This conspiracy interpretation was based not on evidence but on a prior theory that wars are always caused by greedy businessmen . However , the interpretation was popular among left - wing Progressives ( led by Senator Robert LaFollette of Wisconsin ) and among the " agrarian " wing of the Democratic party — including the chairman of the tax - writing Ways and Means Committee of the House . He strenuously opposed war , but when it came he rewrote the tax laws to make sure the rich paid the most . ( In the 1930s neutrality laws were passed to prevent financial entanglements from dragging the nation into a war . ) In the 1930s some journalists pointed to the British propaganda that played on exaggerated tales of German barbarism and appealed to the basically British cultural roots of most Americans . In 1915 , Bryan thought that Wilson ' s pro - British sentiments had distorted his policies , so he became the first Secretary of State ever to resign in protest . He did not , however , blame the bankers . The problem with these explanations is that business supported neutrality . The pro - war element was animated not by profit but by disgust with what Germany actually did , especially in Belgium , and the threat it represented to American ideals . Americans set a standard for German behavior in terms of human decency , political philosophy , international law , and American national interest . Antiwar spokesmen did not claim that Germany was innocent , and pro - German scripts were poorly received . Belgium kept the public ' s sympathy as the Germans executed civilians , and English nurse Edith Cavell . American engineer Herbert Hoover led a private relief effort that won wide support . Compounding the Belgium atrocities were new weapons that Americans found repugnant , like poison gas and the aerial bombardment of innocent civilians as Zeppelins dropped bombs on London . Above all , American attitudes towards Germany focused on the U - boats ( submarines ) which sank the " Lusitania " in 1915 and other passenger ships " without warning " . That appeared to Americans as an unacceptable challenge to America ' s rights as a neutral country , and as an unforgivable affront to humanity . After repeated diplomatic protests , Germany agreed to stop . But in 1917 the Germany military leadership decided that " military necessity " ( i . e . , a chance to win ) dictated the unrestricted use of their submarines . The Kaiser gave the order knowing full well it meant war with the United States — a country that his advisors felt was enormously powerful economically but too weak militarily to make a difference . The political philosophy Americans believed in was a combination of democracy and individualized freedom of the sort exemplified in Britain and France . The alternative to their entry into the war was a world dominated by German political values , including imperialism , militarism , and the suppression of minorities — a guaranteed formula for more wars in the future . Americans wanted a world of peace and democracy ; in 1917 they realized that they must fight Germany to achieve it . One stumbling block was that Czarist Russia — almost as politically repugnant as Germany — was one of the Allies . When a liberal revolution overthrew the Czar in March 1917 , this obstacle suddenly vanished , as war increasingly became the only choice left . Declaration of war . On April 2 , 1917 , Wilson asked a special joint session of Congress to declare war on the German Empire , stating , " We have no selfish ends to serve " . To make the conflict seem like a better idea , he painted the conflict idealistically , stating that the war would " make the world safe for democracy " and later that it would be a " war to end war " . On April 6 , 1917 , Congress declared war . In the Senate , the resolution passed 82 to 6 , with Senators Harry Lane , William J . Stone , James Vardaman , Asle Gronna , Robert M . La Follette , Sr . , and George W . Norris voting against it . In the House , the declaration passed 373 to 50 , with Claude Kitchin , a senior Democrat , notably opposing it . Another opponent was Jeannette Rankin , who alone voted against entry into both World War I and World War II . " Almost all " of the opposition came from the West and the Midwest .