The US entry into WW1 on April 6, 1917. President Wilson had adopted a position of neutrality, this therefore isolated the US from the conflicts in Europe thus this caused it slow entry into the conflict. What sped its response to war was the sinking of the passenger ship Lusitania which was sank by the German warship. The Germans also sank 6 American merchant ships without warning, thus triggering the US to join the fray. The congress held a special session to vote for the favor 373 members over 50.
