In 1917 , three years after the first shots of the war were fired , the United States entered the war and by the end of the conflict more than 4.7 million American soldiers , sailors and Marines would fight in the war .
In 1917 , three years after the first shots of the war were fired , the United States entered the war . By the end of the conflict more than 4.7 million American soldiers , sailors and Marines would fight in the war .