101st airborne
Airborne paratrooper division of the United States Army. Most famous for actions in World War II, especially the 6 June 1944 Normandy invasion (D-Day) and the Battle of the Bulge. They were nicknamed the "Screaming Eagles" due to their unit insignia showing an eagle's head with open beak.
In preparation for the D-Day landings, the 101st painted playing card symbols on the sides of their helmets to assist with unit identification. (As the 101st was the only airborne division to mark themselves thusly, any depiction of World War Two-era US paratroopers with painted symbols on the sides of their helmets can safely be assumed to be the 101st.) A diamond painted onto the side of the helmet signified the 501st Parachute Infantry Regiment, a heart the 502nd PIR, and a club the 327th Glider Infantry Regiment. However, thanks to the popular influence of the book and television show Band of Brothers, most depictions will feature the spade symbol on the helmet that signified the the wearer to be part of the 506th Parachute Infantry Regiment.