apr 6, 1917 - The USA enters the war
The United States joined the war because of the Germans decision to resume the policy of submarine warfare, and the Zimmerman note, intercepted by the British, in which Germany proposed the idea of an alliance with Mexico. The Zimmerman telegram essentially told the Mexicans if the started war with the USA on American territories the Germans would aid them. submarine warfare, was a desperate effort to counter the British blockade of Germany. The Germans ended up sinking of American merchant ships heading for England, and had been employed by the Germans before. Submarine warfares resumption was enough to cause Woodrow Wilson to renounce his stated position of neutrality.
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