2 April 1917. Wilson asks Congress for war to make the world safe for democracy. German U-boats have gone back to sinking ships without warning. British codebreakers have read a German telegram offering Mexico Texas, Arizona and New Mexico. The republic that advertised neutrality is about to send an army across an ocean.
Why then
Loans, munitions and the British blockade have already tied America's economy to the Allies. Unrestricted submarine war is Berlin's gamble that Britain starves before America can arrive. The Zimmermann telegram, published in March, turns the gamble into an insult the public can read.
What they wanted
Wilson wants a seat at the peace more than a casualty list. Ludendorff is betting on starving Britain before an American army exists. Most Americans would rather the war stayed in Europe. They will get a draft, a song and a flu ship.
What changed
America joins as an 'associated power', not an ally, and the distinction matters in Paris. Two million men go over; Germany's last offensives of 1918 are a race against their arrival. The Senate will later refuse the League Wilson designed.
Still argued
Was war inevitable after the Lusitania went down in 1915, or a choice Wilson made after winning re-election on keeping out of it? Historians still split over whether money, submarines or principle decided it.