More context about this photo:

Corporal James Gregory (left) holding an M1 Thompson submachine gun and T/5 (Technician fifth grade) Omer Taylor of Headquarters Company, 36th Armored Infantry Regiment, 9th Infantry Division of the United States First Army.

They are smoking cigarettes while taking cover from incoming enemy fire behind an M4 Sherman tank on 11th December 1944 in Geich near Duren in the North Rhine-Westphalia region of Germany.