I support shortening battles, not for the sake of realism, but for the sake of gameplay. For example, using strategy to gain local superiority means that you can attack an enemy army with more troops than they have defending, despite a larger overall troop count. However, this becomes irrelevant as they can just march troops from halfway across Europe to join the battle and win. This is incredibly stupid and turns every war into a titanic clash of each sides' combined armies. Don't punish tactical and strategic play, reward it.
I agree with the last line, but I disagree that shortening battles would necessarily lead to that outcome (nerfing scorched earth led to that outcome, fort change is a push). Right now, a significant quality disparity can cause complete stack wipes in ~8 days, or shattered retreats within 2-3 weeks typically. More than that and the battle extends more. Part of the reason battles in Europe are drawn out is that terrain such as woods, hills, mountains (the vast majority of HRE land isn't flat) narrow the combat width and extend battles. You can steer armies to avoid that in some circumstances, or catch stacks out far enough to resolve battles before reinforcement. Even with Saxony in my cherry tapping run so far, I showed that a few times while streaming.
If you make battles resolve materially faster than they do at present, attrition micro gets yanked; you will almost be guaranteed to take more damage in fast-ending casualties than you would in attrition even if over-stacking provinces, which means that we'd need to see a rework on how the game provides and handles manpower. It also makes sieging or threatening multiple fronts less viable because the battles are resolved fast enough that threat of reinforcement is trivialized.
Both inside and outside of Europe, I am able to routinely stackwipe forces before the AI can reinforce them. In MP, it's harder to pull off more so because of the tendency for ahistoric giant hugboxing wars that allow routine engagements of troop counts far above the combat width. At most and only in the late game, 80 guys can be actively contributing to the battle per side...but when you hugbox and people run tight formations getting fast shatters, retreat-wipes etc isn't viable. This is also why discipline is more important in MP while it's on a backseat compared to morale in SP (I will go so far as to say that morale inflicts more casualties on average if you micro well in SP, because the AI does not micro well).
