The US entered World War One in April of 1917 but it would take a year before the doughboys arrived in numbers to make a difference in France. At the start of the war the US Army was tiny but by the end of hostilities on November 11th, 1918 over 4 million men had volunteered or been drafted into US Armed Forces.
The pictures below are from Liberty’s Victorious Conflict a post-war (1919) publication that illustrated the war from its start in 1914 to its end in 1918.
The doughboys were welcomed first in Great Britain and then in France. Both countries were exhausted by three+ years of war and they saw America’s entry into the war as the means to break the dead lock.
The captions below speak for themselves but I like the second one best. It features the doughboys in their distinctive campaign hats marching past an honor guard of British Horse Guards in their ceremonial uniform.