Yankees got better and better as time went on. That's why Napoleon advised not to fight the same enemy to often, he will learn you. Notice the plains Indians were getting better at fighting the U.S. Army until Grant and Sheridan decided to wipe them out before eastern politicians became ''woke''. That was beginning to happen. After the costly victory at Little Bighorn and the successful Indian escape the U.S. knew they had to wind up the Indian issue pretty damn quick. Bleeding hearts back east were making noise about ''the poor Indian".
