There was the Napoleonic era, and WWI, and... it doesn't seem like there was a lot in between. For actual wars between states, I can think of the Italian Wars of Unification, Franco-Prussian War, Austro-Prussian War, maybe Belgian Revolution, sorta... that's about it. Those wars in themselves weren't small, but they were all clustered towards the middle of the time period, and all ended fairly quickly (and weren't as famous and thus studied as other wars like WWI). Anyway, it's not a lot of war compared to the 18th or 17th century, and there's that idea that Napoleon send columns of infantry until the British mowed them down, and yet it still happened with machine guns in WWI. So, all throughout, but particularly in the earlier period I guess, how did European tactics change, and from what to what?
Hey, this previous answer may be of use! :)
Respond if you have any further questions!
As for the claim that men 'marched into machine guns' et al, I'd check out this thread.
To add to /u/elos_, these answers I've given should also be pertinent
and there's that idea that Napoleon send columns of infantry until the British mowed them down
This is a myth of the Napoleonic Wars, particularly the Battle of Maida, that seems to originate from the great British Historian of the wars, Charles Oman. The French deployed in lines at Maida, and line and column (Ordre Mixte) were widely used by all sides in the war. /u/elos_ has the 'marching into machine guns' myth covered, to which I would add that Paul Cornish's Machine Guns and the Great War is an excellent recent work on how Machine Guns actually functioned in the Great War.
Thanks to both of you! Those links are very useful. Would it be accurate, then, that warfare in Europe changed relatively little from Napoleon's time onwards, until the invention of the Dreyse needle gun?