True, but I've always been fascinated by how long it took for people to understand this. Fifty years after Gettysburg, the British suffered 60,000 casualties on the first day of the Battle of the Somme.
they didnt march into the fire at the Somme like they did at Gettysburg. There wasn't any marching as such and it wasn't the Napoleonic school at the time....
at the Battle of the Somme, they used an early and horribly thought out version of the loose order drill that was used very successfully in World War 2.