What are some lessons from the Civil War?

Answer 1

One that was a long time in sinking in is this: if your enemy is entrenched, and equipped with rifles, it is extremely costly to send your own men running at his positions in a frontal attack. This is a very bloody approach to the problem, and, seven times out of eight in the Civil War, it did not work. All the officers of both sides had studied at West Point and learned all about Napoleon. But in Napoleon's time the soldiers had inaccurate, smooth-bore muskets. In the US Civil War they had much more accurate, rifled weapons, with a much greater range. Trying Napoleonic tactics against this improved weaponry resulted in mass carnage. Commanders on both sides were slow to learn.

What's more inexcusable, though, is the fact that the European generals learned nothing from this lesson. They considered that there was nothing instructive for them in the American Civil War, which they believed amounted to two armed mobs chasing each other around in the woods. Nothing there applicable to Europe.

So, fifty years after the American Civil War ended, having largely been at peace for a century, European generals of every nation eagerly, bravely hurled their soldiers at the entrenched foe, who now had not a single-shot muzzle-loading rifle capable of three shots per minute in the hands of a trained man, but machine guns capable of firing six hundred shots per minute. Of course the slaughter was incalculable. But, unlike the generals of the Union and Confederate armies, the Europeans two generations later NEVER learned any better.