This isn't explained anywhere else online, so here goes.
The data is based on data files from the latest patch. All of it comes from campaign_difficulty_handicap_effects_tables db table, so mods can adjust it.
Player Bonuses and Penalties
Difficulty levels rely mostly on buffing AI, so player penalties on hard and very hard are fairly small, and bonuses on easy aren't that big either.
| Bonus | Easy | Normal | Hard | Very Hard |
|---|---|---|---|---|
| clamour for reform all classes | -1 | |||
| cost - buildings - all | -10% | |||
| cost - recruitment - land | -30% | -25% | -10% | |
| cost - town watch | -10% | +15% | +30% | |
| cost - upkeep - land | -20% | -15% | ||
| cost - upkeep - naval | -30% | -15% | ||
| counterspying | +2 | |||
| max population | +10% | |||
| max repression - government type | +1 | |||
| personal security | +2 | |||
| research rate | +15% | -5% | -12% |
AI Bonuses and Penalties
AI bonuses on the other hand are very extensive.
| Bonus | Easy | Normal | Hard | Very Hard |
|---|---|---|---|---|
| agent cap - eastern scholar | +1 | +2 | +2 | |
| agent cap - gentleman | +1 | +2 | +2 | |
| agent cap - missionary | +1 | +2 | +2 | |
| cost - buildings - farms | -8% | -20% | -30% | |
| cost - buildings - happiness | -8% | -20% | -30% | |
| cost - buildings - industry | -8% | -20% | -30% | |
| cost - buildings - mines | -8% | -20% | -30% | |
| cost - buildings - plantations | -8% | -20% | -30% | |
| cost - recruitment - land | -10% | -20% | -30% | |
| cost - recruitment - naval | -8% | -15% | -23% | |
| cost - town watch | -20% | -50% | -90% | |
| cost - upkeep - land | -30% | -40% | -50% | |
| cost - upkeep - naval | -25% | -40% | -50% | |
| counterspying | +1 | +2 | ||
| GDP | +10% | +20% | +40% | |
| max population | +10% | |||
| max repression - characters | +1 | +2 | +3 | |
| movement points | +10 | +15 | +20 | |
| personal security | -1 | +1 | +2 | |
| recruitment cap - land | +1 | +3 | ||
| recruitment cap - naval | +1 | +4 | ||
| research rate | +10% | +35% | +50% |
Diplomacy
Diplomacy is definitely affected by campaign difficulty, but the logic is hardcoded, and not exposed anywhere. On harder difficulties AI has a massive and very obvious anti-player bias.
What is not affected by difficulty
And that's all. A lot of things difficulty affects in other games (including other Total War games) are not affected by difficulty level. This means all of these are the same regardless of difficulty levels:
- starting armies
- starting buildings
- starting research
- starting diplomacy
- starting income
- fixed income per turn
How to overcome difficulty bonuses
Campaign difficulty modifies just a few areas, and in each of them, there are very strong counters available.
Research rate - AI on very hard has +50% while the player gets -12%. However AI typically only has 1 school, while you should build 4-6. If you have enough patience, you can also trade techs, something AI doesn't seem to do much. You will outtech all AIs with ease. AI's extra diplomats and scholars also come nowhere near matching the advantage you have by just having a few more schools.
For diplomacy bias, giving away military access to everyone on the map (at least everyone you border, plus countries like Britain and France who love to drop surprise naval invasions on you) really tones AI aggressiveness down to more reasonable level.
AI gets a lot of different bonuses which are basically money cheats. The best way around it is by being better at economy game. If you can, spam trade ships. And never have a big expensive army just sit there doing nothing, something that AIs routinely do. Your main army should go on an offensive. If you need long term garrison, just recruit some cheap crap instead, or units with garrison bonus.
You can also use AI bonus cheat against itself. Especially all the one province minors have nothing to spend their money on, so they upgrade all their buildings as soon as possible. And then you can conquer them. A maximally cheesy version of this strategy is to sell AI minors farm and industry techs they need to unlock the upgrades, and maybe even sell them your worst provinces that need a lot of money to turn around. Then conquer them once they're fully upgraded, and all you'll need to pay is the repair bill.
AI gets some happiness bonuses you don't, but it doesn't really affect you, as you're not trying to out-happiness the AI. You should definitely get better at happiness game, which for absolute monarchies means stacking your cabinet with ministers with as many lower class happiness bonuses as you can. But you should do so regardless of how happy AI provinces are.
AI's extra movement points can take you by surprise - sometimes enemy army is just barely out of your reach, so you think they can't reach you either, then you get surprise attacked when you press end turn. As long as you're aware of it, it isn't usually a big deal. And AI movement cheats have nothing on daisy chaining ships to transport your stacks from one end of the theater to the other in one turn.
And this just leaves AI's huge +3 recruitment cap bonus on very hard (+1 on hard it's no big deal). It can outspam your units with ease. The trick is that while recruiting new units is capped, replenishment is unlimited and just costs money and two turns. So if you have a lot of badly battered units after a big battle, as long as none of them got wiped out, you can get your whole stack back really quickly - something that wasn't possible in earlier Total War games.
Another useful trick is just recruiting a lot of new units in far away lands, and using ship daisy chaining to transport them to where you need them to be.
Naval recruitment cap is technically even bigger, but AI doesn't really spam ships anyway.
Autoresolve
Empire's autoresolve is a black box. There are some difficulty-related settings in campaign_variables_tables, but what they do exactly is anyone's guess:
- autoresolve_easy_campaign_AI_percent_reduction - 0.05
- autoresolve_easy_difficulty_human_advantage - 0.1
- (no settings for normal)
- autoresolve_hard_campaign_AI_percent_increase - 0.2
- autoresolve_hard_difficulty_AI_advantage - 0.08
- autoresolve_very_hard_campaign_AI_percent_increase - 0.35
- autoresolve_very_hard_difficulty_AI_advantage - 0.2
As far as I can tell, autoresolve bonuses are controlled by battle difficulty, not campaign difficulty.
You can mod these to -0.99 if you want free autoresolve wins for some testing. Or if you really hate naval combat so much, and plan to only use it for naval combat.
Battle difficulty
I wanted to provide similar data for battle difficulty, but I couldn't find any game files controlling it. This likely means that the battle difficulty is implemented as part of game logic, and possibly in a way more complicated than just simple stat boosts.
We have some idea what is affected the most. AI troops on hard and very hard get a huge morale bonus, which is a huge nerf to player's melee units, especially melee cavalry, which normally relies on breaking enemy units' morale, and has poor staying power in prolonged battle. Bonuses to accuracy and reload speed are more modest, and for artillery difficulty levels seem to matter the least.
However, it's difficult to put any numbers on these qualitative statements.
And that's all we know about Empire Total War difficulty. If you find out any additional numbers (by reversing executable file?), let me know.
