These pattern combat boots where introduced by the US Army in June 1943 and where the standard boots issued to the US Infantry. They would have been worn during training in England and during the D-Day invasion in Normandy in June 1944.
The roughout boots where the standard footwear for the US Army in World War Two and gain there name from the fact that the leather uppers are reversed so that the "flesh out" side (the rough side) is on the outside and the smooth leather is on the inside.
The roughout boots where worn with the M1938 canvas gaiters. These service boots with reverse uppers could be worn with the likes of the HBT trousers and the M1937 wool trousers around camp, in the field, in combat and as part of the A class uniform.