Its ironic that the Civil War began using tactics of Napoleon 50 years before, and ending using tactics of The First World War 50 Years Later.
I once heard the Civil War described as a 19th century war fought with 20th century weapons and using 18th century tactics. The Prussians learned a lot by observing our Civil War, and then used that knowledge to win the Austro-Prussian War and the Franco-Prussian War. ....and after all of that, the Brits and French (and Germany cavalry) still used mid-19th century tactics to destroy millions of their own troops.