EU3 Combat System? Oh no...

[Chaingun]

If you want the game to be playable without annoying pauses by many people in multiplayer this is a necessary exception to realism. Since the basic time unit is a day most battles would take only 1 time unit to complete. That would equal around ~1 second (more or less depending on game speed) of reaction time. Strategic decisions such as retreating or reinforcing in battle can't really be performed by a human in that amount of time. You can only fix this by fooling about with the global time scale, but that will make multiplayer annoying. Slowing down the game for a battle between two players will ensure the ones who are not fighting will have a very boring time.

Then again, it would perhaps be ultra-realistic for a country/faction/citystate leader not to be able to detail-control troop retreats or reinforcements. However, this will reduce battles to instantaneous dice throws for the player, and will remove quite an exciting bit of gameplay. I personally enjoyed detail-control of combat in EU2 (and to some extent EU3). I'll even say for me fighting wars was best part of game.

 

[Chaingun]

I hate EU3 combat system because enemy armies keep bouncing after every defeat, no matter how many times. And sometimes they immediately run away when they have 1 soldier left in their army, and you have 1000. And you must keep chase them for years. How crazy is that?

That's a side effect of EU3's regiment system. When a regiment dies in EU3, you have to purchase a new one with ducats and manpower. A regiment surviving (even with 1 man) will only require manpower to reinforce to full strength. That makes any losses of complete regiments extremely expensive. Thus Paradox probably wanted to make the experience less frustrating and expensive (for the loser) by making the battle logic lenient to losing regiments. Otherwise winning battles would be much more effective than it is, since the winner would have all regiments survive and be able to just reinforce, while the loser would have to pay ducats to replace his destroyed regiments. This does lead a lot of silliness however, as "bouncing" occurs and the attacker will take much larger casualities to attrition if he has to follow back and beat enemy regiments deep in their territory to completely destroy them.

Compare to EU2 where troops aren't organized in regiments: there is no reason not to let the battle logic destroy a 10 man army losing (although during extreme circumstances you could still have 10 men survive a battle). You have to pay ducats and manpower regardless since your army will not automatically reinforce.

It's also interesting to note it's the basic reason why EU3 warfare costs less ducats than warfare in EU2. In EU3, once you built your army, it will take very little ducats to keep it reinforced (excluding maintainence costs of course).

CK also has like EU3 regiments but it's better in one way; since you have 1 regiment per county a regiment can be destroyed somewhere but rebuilt back in the county. So losing an entire regiment isn't as critical and thus easier to justify in the battle logic.