They stayed behind
This 1928 photograph captures the marble crosses in Block B of the 42-acre Aisne-Marne American Cemetery near Belleau, France. Of the 2,288 American soldiers buried here, 251 are unidentified. Most of those buried here lost their lives forcing the Germans to abandon their positions near Aisne-Marne in July 1918.
National Archives, Records of the American Battle Monuments Commission