In one scene the Doughboys are trapped at night by artillery fire out in No Man's Land. The next morning they are suddenly in a wooded area with trees, buildings, and a vineyard.
The helmets the WW1 Doughboys are wearing are M1917A1s. These were introduced after WW1.
Nurse Tommy mentions that she will be transfer to a hospital in Toulon. The town is situated in southern France, about as far from the front as one could get.