Investigation of Battle Odds

[Atilius]

dismal,

You've pretty comprehensively demonstrated the strength ratio/battleOdds connection, that a Heroic victory requires more that just killing all the enemy without any losses of your own, and the Son of Chinglu stuff.

The last item provides a nice illustration of how of the event triggers work.

Anyway, you've put paid to the discussion we've been having about these topics, so I went back to the first real post in this thread:

I wonder if someone could research the factors that determine the strategy map battle odds? I imagine things like number and quality of men, upgrades, commander, and so on.

This seems to be important for getting traits, whether the AI will fight, etc.

I'm planning to look at the effect of a commander's battle stars on battleOdds. Anyone's welcome to scoop me.

[dismal]

dismal,

You've pretty comprehensively demonstrated the strength ratio/battleOdds connection, that a Heroic victory requires more that just killing all the enemy without any losses of your own, and the Son of Chinglu stuff.

Yep, a lot of this started in my effort to figure out what generated a Heroic victory. The "chinglu" thing was a bit of a diversion, but at least its 100% chance factor helps give a little clarity into a few game variables.

I need to go back and revisit the "Heroic" victory question. I can't help but wonder if it's as simple as BattleOdds (= strength ratio) <1 combined with some minimum percentage of enemy killed and some maximum percentage of allies killed.

I'm planning to look at the effect of a commander's battle stars on battleOdds. Anyone's welcome to scoop me.

You could quickly generate some data using something like the approach I used above.

1) Start new campaign w/ fow and AI moves off
2) Take a general and move him within one turn of a battle.
3) Save game
4) Initiate battle, check odds
5) Quit and Reload saved game
6) Mod general's command up/down
7) Repeat beginning at step 4

The added benefit here is you don't actually have to fight the battles.

[Atilius]

OK,

I got around to looking at how a general's battle stars affect the strength ratio/battleOdds you see on the strength bar before combat. The results are not as I'd expected.

I'm running RTW 1.3. To start, I set up a couple of small armies (2 units of hastati, no experience, no upgrades) with a Roman general. The generals each have only the Confident commander trait and no ancillaries, so each has one star. The strength ratio is 1:1 - no surprise.

Next, I remove the the GoodCommander trait from the defending general. Odds are 1:1, but this could skewed by the presence of the opposing forces' bodyguard units, so I give each army 19 hastati to dilute the effect of the bodyguards. Odds are still 1:1.

I give the attacking general the Legendary Commander trait (5 stars), defending general still has no stars. Odds are 1:1.

I give the attacking general the Heroic Attacker trait too, so he has a total of 10 stars when attacking. Odds are 1:1.

Finally I give the defending general the Pathetic Commander (-5) and Pathetic Defender (-5) traits. I'm pretty sure that these only subtract from command stars that the general may have gotten from other traits or ancillaries, but I do it anyway. Odds are 1:1.

Also reversed the situation, giving the attacker penalties (Pathetic Commander, Pathetic Attacker) and the defender bonuses ( Legendary Commander, Heroic Defender), but odds are always 1:1.

So it's clear that the calculation of battleOdds takes no account of the opposing commanders' battle stars. I believe the main effect of battle stars is to raise the morale of the general's army, so Jerome's comment earlier in this thread:

The battle odds are based on the AI's strength calculation for the armies involved. Essentially this is a number derived per unit via a complex formula which takes into account the number of soldiers, attack, defense, experience, upgrades, morale, and almost everything else which gets fed into the game from the export_descr_unit.txt file.

must refer to the unit's un-modified (dismal, here I go with the un-modified thing again) morale value (from export_descr_unit.txt ) and not to any morale bonuses gained from the general's battle stars.

[dismal]

I guess I'm not completely surprised that command ranking doesn't affect battle odds.

Since you rasied the topic, I had noticed that clicking the "night battle" option (when available) didn't change the battle odds despite increasing the general's command stars.

[Atilius]

I spent some time investigating how unit experience influences battle odds.

I have two armies, each consisting of 20 units of hastati. At first I vary the experience of the attacker ( note exp 1 = 1 bronze chevron, exp 4 = 1 silver
chevron and so on):

Attacker Exp Defender Exp Battle Odds
0...................0 ............. 1:1
1...................0 ............. 6:5
2...................0 ............. 6:5
3...................0 ............. 6:5
4...................0 ............. 7:5
5...................0 ............. 7:5
6...................0 ............. 7:5
7...................0 ............. 8:5
8...................0 ............. 8:5
9...................0 ............. 9:5

Reverse the experience values just to make sure odds reverse also:

0...................9 ............. 5:9

It looks like we are getting some round off, but taking this into account it appears that a unit becomes ~10% more effective for each additional level of experience.

If this is the case then if one army has experience 8 and the other 4, we'd expect the odds to be 1.8:1.4 (9:7). If I try this I find the odds are actually 9:8. Rounding? If I try exp 9 and exp 4 I'd expect 1.9:1.4 (9.5:7), I actually get 9:7.

Anyway, this seems to indicate that the ~10% incease per experience level (perhaps slightly less) is approximately correct.

I did one other check on this: How many exp 9 units does it take to make an even match for 20 exp 0 units? If the above is correct, the answer should be 20/1.9 which is slightly closer to 11 than to 10. If I set up a battle with 11 exp 9 units against 20 exp 0 units, I get battle odds of 1:1.

So a good rule of thumb is that each level of experience increases the unit's effectiveness by 10% of the strength of a 0 experience unit.

[Atilius]

I was looking for something useful to do this evening, but decided instead to have a look at the effect of armor on battle odds.

Setup: RTW 1.3, two armies of 20 hastati each.

Possible armor values (AV) are:
0 (no shield),
1 (bronze shield),
2 (silver shield),
3 (gold shield)

Results:

Attacker AV Defender AV Battle Odds
0 ............... 0 .................... 1:1
1 ............... 0 .................... 6:5
2 ............... 0 .................... 7:5
3 ............... 0 .................... 8:5

I also reversed the AVs (attacker AV 0, defender AV 1,2,3 ) and got reversed odds as you'd expect.

These numbers indicate that each armor upgrade increases the effectiveness of the unit by about 20% of the effectiveness of an AV 0 unit - at least to the battle odds calculator.

I ran another test to check this conclusion. If the above statement is true then how many AV 3 units are required to balance 20 AV 0 units? The answer should be 20 * 1.0 / (1.0 + 3 * 0.2 ) = 20 /1.6 = 12.5.

# AV 3 units # AV 0 units Battle Odds
11 ............... 20 .................... 4:5
12 ............... 20 .................... 1:1
13 ............... 20 .................... 1:1
14 ............... 20 .................... 6:5

SO: each armor upgrade increases the effectiveness of the unit by about 20% of the effectiveness of an AV 0 unit.

[magnum]

Any chance that you could run the same test(s) with different attack/defensive values than the Hastiti does? Wondering if its 20% or if the calculation is actualling feeding in the numbers, in which case a lower defense the armor upgrade would be more than 20%, a higher defense the armor upgrade would be less than 20%.