This is a uniform shirt worn by a Corporal in the ADSEC unit of the 1st INF, US ARMY.
The ADSEC patch represents the Advance Section, Communications Zone, European Theater of Operations, Army. It was created February 1944 and attached to the US First Army. It moved forward with the army and provided close support, particularly in the invasion of Normandy, D- Day. Besides bringing in supplies for the advancing armies, the men also rehabilitated railway rolling stock and provided transportation of gasoline. The units also included field hospitals, and operated blood banks.
The Big Red One patch stood for 1st Infantry Division. Also called the Bloody First, their motto was No Mission Too Difficult, No Sacrifice Too Great- Duty First!
The First took part in the combat amphibious assault of North Africa, and then invaded Sicily, afterwards returning to England to later take part in the Normandy invasion at Omaha Beach.