But briefly, the officer in question refused to solve a shortage of Union arms at the start of the war by buying a bunch of surplus British Enfields, which were actually better guns that what the Union had at the time. (The US Army did have some muzzle-loading rifles like the Enfield, but most of them were located in southern armories.) One reason he declined was that it would be "unpatriotic" to by British arms.
The South, on the other hand, had no such qualms, and snapped up all the Enfields.
There's more, but I don't trust my memory that well.