One reason why the American Civil War was so perversely fruitful in the improvement of military technique was because it was mainly a war of amateurs, who were fairly representative of all the talent that the community could muster, and who were not inhibited from applying their wits to military affairs by the cramping effect of a hide-bound military tradition. The majority of our great Western wars in the Modern Age have been fought under the command of professional officers; and some instinct of self-preservation has inspired our modern Western Society to recruit its military officers from among its less able members, and then to cripple the abilities which they possess by a rigid routine. The exception which proves this rule is the school of professional officers in Prussia who won the European wars of 1864-71 .
“Lions led by donkeys” (Wikipedia).
A Study of History, Vol IV, OUP, 1939 (footnote)