The obvious answer is that is was taken to France after D-day, since a huge amount of supplies and especially fuel had to be taken forward from the ports to wherever the Allied armies had got to - Belgium in need be. French railways had been damaged by a lot of actors - e.g. the
RAF▸ and the resistance, as well as the Germans.
Christian Wolmar had a book out on this subject last year, which
he gave some details from in this article:
Two thirds of the three million tons of supplies that passed through Cherbourg were carried forward by rail. Some 1,000 US and 1,000 UK▸ locomotives were shipped over, along with 20,000 freight wagons, in order to replace stock destroyed in the conflict or stole by the Germans. At least 50,000 men, both UK and US soldiers, worked on repairing the lines often under the most difficult conditions imaginable. The Americans created no fewer than 50 railway operating battalions, each linked to a particular railroad company, to run what became, for a time, Europe’s biggest railway network, controlled by the military with the principal purpose of furthering the war effort. More than 1,200 Bailey Bridges, a system developed by the British but also used by the Americans, were constructed, principally for use by the railways.
