This is a recruiting poster geared toward encouraging African American men to enlist in the US Military during World War One. Notice them conquering the Germans with a benevolent Abraham Lincoln looking on. At this time in American History African American soldiers were known as Buffalo Soldiers, a holdover from their time in the US Cavalry in the West. It is commonly believed that the term Buffalo Soldiers came from the Native Americans, either in reference to their bravery or perhaps in reference to their hair.
Buffalo Soldiers were not allowed to fight as part of the American Expeditionary Forces, but the 92nd and 93 Infantry, comprised of African American soldiers, was seconded to the French for the duration of the war and fought under the French Command, some of the first Americans to engage in conflict in The Great War.
The historic African American Buffalo Soldier unit the 10th Cavalry supported the 35th Infantry in the border skirmish known as the Battle of Ambos Nogales in which German advisers fought alongside Mexican soldiers, the only battle of World War One where Germans fought on North American soil.
Today in history marks the beginning of the Third Battle of the Aisne, 1918, a battle in which US African Americans fought.