During the American Civil War Ohio cotton traders were going down river and buying Confederate cotton in exchange for gold. Grant and Sherman tried to stop it but were over ridden by the White House. In the Franco Prussian war of 1870 Prussian stocks and bonds were being traded on the Paris Bourse and vice versa on the Berlin exchange. In addition, trade was conducted between the two belligerents. Nothing stops money.
The Civil War analogy is an apt one.
I never knew how much profiteering went on during that war until I started researching it a while ago.
Perhaps the Union needed the cotton for its war effort. I can imagine that wool underwear would be awfully uncomfortable for soldiers in the field.