This soldier is a member of the 343rd Field Artillery Regiment. He had this picture taken in The States. The 343rd served in France and participated in the St. Mihiel Operation and the Meuse-Argonne Offensive.
The writing on the backs reads "Adm. D. B. Wilson + Capt. G. C. Day turning the Pennsy over to Father Neptune (C. W. T. Sheehan)". Admiral Henry Braid Wilson was the commanding officer of the USS Pennsylvania in 1916. I believe he is the officer on the left, receiving the line of costumed characters.
These six German soldiers are posing with an unexploded 38mm shell that they have written "Ein Gruß aus England" which translates to "Greetings from England". The faint writing at the bottom places them at Minacourt in 1917.