Pewt you need allies, 2 vs 1 can easily turn into 3 vs 1.....
Easier said than done; nobody is interested in joining my side for fame or fortune. That said, other people have other rivalries, so a 3v1 has a much better chance of becoming a 3v2 than a 2v1 does of becoming a 2v2.
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Since so much of the game’s basic combat mechanics are not very well understood, here’s an explanation of the simpler bits. I’ll be talking strictly about land combat, since it’s both more complicated and more important. Maximizing every value mentioned here is important, and they have a surprisingly huge effect on how well your armies perform compared to how small some of them seem.
What information do I have about a battle in progress?
Here’s an example battle to reference:
The attacker is on top, the defender on the bottom. Each side has a total troop count, a general, a combat modifier box, and a morale bar. The first two are straightforward. The combat modifiers are as follows, and the final modifier for each side is the sum of all modifiers on that side (so all modifiers with equal values are equivalent):
The roll, from 0 to 9. This is updated to a new random value every time the combat’s phase changes.
These general-derived die modifiers are applied to the side with the better general for that phase, and is the difference between that general’s fire or shock value and the others’. Note that once a general is selected, later-arriving better generals will
not replace it unless the original general’s army leaves the fight.
The terrain penalty. This is always applied to the attacker and can range from 0 to -5, depending on how harsh the terrain is. When a combat starts, it has a percent chance to occupy any terrain type in a province (visible on the terrain mapmode) based on the percent of the province which contains that terrain. This number is selected on round 1 and remains unchanged for the rest of the combat.
The crossing penalty, ranging from 0 to -2. Crossing a river costs the attacker 1 point, while crossing a strait or unloading from ships costs 2. Note that, if I recall correctly, it is possible for these to change mid-combat based on new armies arriving, but only for the worse.
Combat modifiers are not the only thing that influences how much damage your armies deal and take, but they’re the only one which can vary by battle with all other things remaining the same.
The morale bar is the average morale of units on the battlefield compared to the maximum morale of the highest morale unit in either army. It can fluctuate wildly as armies participating in the battle enter and leave the battlefield, and over all isn’t very useful.
On the top left we see a flag telling us that it’s impossible to retreat from the battle. This lasts 4 phases.
Finally, closer to the middle we can see both sides’ battlefield layouts and which phase it currently is (Shock or Fire). The phase changes every 3 days and begins with fire. The battlefield layouts are relatively complicated and not very important, but it’s useful to know that as deployed unit counts dwindle on the battlefield it’s an indication that you’re running out of morale, since units with 0 morale cannot fight. When your morale bar suddenly fills up, it’s due to a new wave of units on the battlefield. Mousing over a unit’s square on the battlefield will tell you which regiment from your army it is.
What information do I have about leaders?
Here’s an example leader pane for reference:
Tradition tends to decay yearly, although you can get regeneration from Battlefield Commissions, War College, Veteran’s Home, The Last Jousting Tournament, an Advisor, and a few other sources. As a general rule, each point of yearly army tradition moves your stable (no net gain/decay) tradition by +33%. It is mostly gained by fighting battles and completing sieges. Hired generals’ stats are largely determined by it, and as a general rule generals with less than about 30% army tradition will be underwhelming while generals with over about 60% army tradition will be excellent.
Generals have four values: fire, shock, maneuver, and siege, the first three of which are rated from 1 to 6 while siege is rated from 1 to 3. Fire and Shock determine the general’s modifier during the corresponding battle phases. Maneuver primarily affects an army's move speed on the world map and vulnerability to attrition (stack weight). Siege affects the time between siege progress events and the chance at good ones, but is not very useful overall.
Discipline is also on this tab, although it has little to do with generals. Your army has a discipline value, affected mostly by advisors, the Quality vs Quantity slider, and the Militia Act, although certain nations get special decisions and there are a few other modifiers. You can think of discipline as your army’s percent effectiveness, with 100% being average.
Finally, Military Tactics is another value sort of like discipline; it's only listed very inconveniently in the ledger, but since it ties in nicely to discipline I’ll mention it here. It starts off at 0 (1 if you keep less than the cavalry maximum in an army), increases at certain tech levels, such as 18, and reduces your losses in combat significantly.
What information do I have about my troops?
The Military tab has a fair amount of information:
On the top, you’ll see your currently selected Infantry, Cavalry, and Artillery types, which are the units your core provinces will offer. Each one has its own Fire, Shock, and Morale rating, with both Offensive and Defensive substats. For the most part, you can treat Offensive and Defensive pips as the same field (so total Shock = Offensive + Defensive), and Morale pips are seemingly rather unimportant in comparison. Which of shock or fire is better depends on your generals and modifiers.
Beside the unit type selected, you’ll see how many of that unit you have, as well as your shock and fire multipliers. These multipliers are a mostly hidden value which increases nonlinearly with tech, and have an absolutely massive effect on how much damage you deal; for instance, they’re why Fire damage is so weak until Land tech 22 and still much weaker than shock for a few more levels, as well as why Cavalry are so strong despite their seeming lack of pips. You can’t control them in any way other than increasing them with tech, but being aware of which Land tech levels yield important modifiers can be critical to winning a close war.
Here’s a reference list. Looking at this list makes some things such as the huge jump in unit power from Land tech 9 to Land tech 11 much more intuitively obvious.
At the bottom, you’ll see your Morale, Force Limits, and Maintenance. Maintenance determines your reinforcement rate as well as adding between 0 and 2 points to morale. Your force limits apply a modifier to maintenance, with your total maintenance being equal to (base maintenance * Max(1, force limit/unit count)), which causes maintenance to skyrocket if you’re much over your force limit, since each additional unit penalizes every existing unit as well as itself. Mousing over morale stars and force limit gives you a breakdown of where they’re coming from, which can be highly useful in determining why your morale is so far behind someone else’s.
Anyhow, hope this helps. This isn't a totally in-depth look at the systems, but this is all you particularly need to know to perform well in land combat.