I have heard it said that the belligerents at the outset of ww1 were not prepared for how warfare had changed due to the advances in weaponry and that the leadership would have done well to look at the American Civil War to get an idea of how warfare had changed.
The first part of the statement is true to my understanding but I am wondering about the pervasiveness of that unpreparedness for how warfare had changed. Were there individuals or groups that spook up before ww1 began in earnest about how it would be fundamentally different? Additionally, was the aforementioned unpreparedness due to complete lack of recognition of how the new weapons would change warfare, or was it a case of the change was recognized but not the degree to how much it changed.
The latter part of the statement about the civil war I find to be much more suspect for a few reasons. First and most significantly the Civil War was a significant war and have a hard time believing that European generals and other leaders would not have studied the war in both its warfare and its effects on society and the economy. Second and less significantly, the civil war was nearly 50 years in the past and several other more recent wars I would have thought to be better for viewing how warfare had changed in practice though not the influence of the wars on the civilian population. The one that strikes me as most likely to be looked at would be the Russo-Japanese War but there are a few others that I would have thought to be at least somewhat indicitive: Spanish-American War and First Balkan War.
As a hanger-on question, was American military leadership surprised about the changes in warfare?
Yeah...there goes the "Donkeys" thesis, raising its head again. Not your fault, though - Basil Liddell Hart and those who followed did a lot of damage regarding our understanding of the First World War.
So, at the beginning of WW1, the generals across the board WERE aware of how warfare had changed, and it scared the hell out of them. During the Russo-Japanese War of 1904-1905, the European powers had military observers present, and these observers published what they had seen in the very active military journals. The Russo-Japanese War - a war between two modern military powers - was a modern trench war and a bloodbath. And, this was reported.
If you do a survey of the military journals between 1905-1914, there is a near- to total obsession with figuring out how to deal with trenches...and nobody really has a good answer. In the light of this, it becomes very clear that the hyper-aggressive war plans were not a sign of generals being disconnected from reality, but of generals desperate to avoid a trench war, and using winning before one can start as their strategy.
Once the war actually bogged down, the generals were stuck in an impossible situation - breaking into a trench system was actually relatively easy, so long as you prepared the enemy trenches with artillery and small arms fire, but, due to limitations in communications and transportation technology, turning that into a breakthrough was nigh-impossible, as by the time the reserves knew that a break-in had been achieved, the enemy had invariably retaken and re-fortified their lines.
So, the idea that the belligerents in World War I were unprepared for how modern warfare had changed is basically pure myth. They were well aware of it, had been seeking solutions for around a decade before the war started, and been left between the proverbial rock and a hard place.
(About 11 years ago, I wrote a term paper on this that quotes a number of the military journal articles - it's not peer-reviewed, but that shouldn't be too much of a problem considering that it is primary source research...so here's the link, if anybody wants to read it: https://drive.google.com/file/d/1sy04uweQ45s5GFY0E2F_O7UfQ8vYRhWm/view?usp=sharing )