The American Civil War was our first encounter with industrialized warfare on a massive scale; for much of Europe, that came in WWI. The earlier wars (Franco-Prussian, Austro-Prussian) were settled too quickly for them to understand how warfare had changed.
The trench mutinies of 1917, which were hidden from the Western public at the time, came about when French troops realized their lives were being thrown away needlessly by elderly generals with no concept of how warfare had changed. Two decades later, the offspring of those French troops refused to be conned again; Germany took France in weeks because a new set of aging French generals were prepared to go to war “1914-style”.
Even after the first grim, horrific months of trench warfare and thousands of deaths from soldiers marching into machine gun fire, they still had generals, like British commander Haig, who thought cavalry could work against fortified machine gun positions. In that war the generals were generally dumber than the pols.
One of the people who did see the futility of fighting a modern war with obsolete methods was Churchill. He was maybe the first person to advocate the use of tanks to defeat the trench warfare system and the machine guns. Naturally, it wasn't until much later in the war that tanks were used extensively.
But, of course, Churchill is maligned for his supposedly bad plan with the Gallipoli campaign. If Churchill had been given full charge, the plan most likely would have worked. Churchill never planned for an army landing and trench warfare.
He devised a naval assault on Istanbul that would probably have worked and knocked Turkey out of the war. With Turkey out of the war Germany would have had one less ally and other countries in the area might have been encouraged to support the Allies against Germany.
An initial naval assault up the weakly defended straits had wreaked havoc on the Turks and almost caused them to abandon Istanbul.
But the Allied generals in charge delayed action and refused Churchill's request for a large naval assault on Istanbul. Instead, they delayed and settled on an army invasion of the lower peninsula. By that time, with the help of the Germans, the Turks had fortified the area. Another naval assault would probably have worked again, but again Churchill was turned down.
So he gets all the blame for a campaign that was basically screwed up by the army chiefs who didn't like Churchill. All this is from William Manchester's "The Last Lion" a three volume bio of Churchill.