Faction Power, what is it

I do know unit, number of city do cause power rating, but I'm not sure about leveling, but attack and armor rating might cause power rating...

It's mostly to do with how powerful your units (champions and regular army) are.

# of cities, population, research, etc. also count towards it.

Something bear in mind though is that (as I've said several times) your power rating has nothing to do with your actual ability to wage war.  Your mana stockpile isn't taken into account for one thing.  If your enemy has conveniently placed all of his military units in one place you can wipe them all out without firing a shot.

It also doesn't take into account just how quickly you are able to replace lost units.  When you get Arcane Forge enchantment going on a high-essence fortress you may practically be doubling its production capability.  Suddenly you go from struggling to crank the units out to woosh, there's your army.

I'm pretty sure it doesn't have anything to do with economical power/ number of cities. My power level doesn't go up or down when I conquer r lose a city. It's purely your military power, however the game calculates that.

I've asked repeatedly about this, without any response from the development team.  I guess they don't want us to know, which seems silly as it wouldn't make the game any easier to understand exactly what makes a faction rating higher, or lower.

All we know is: world achievements may help out.  Having more military, and earlier, definitely seems to help out.  More cities, and more heroes, helps.  Research and popuiation appear to help.  Probably none of this is simply a simple direct value, but who knows?

My preferred strategy in 4X games is to max research and tech, while making large production centers, and then cranking out powerful units once an AI declares war on me. I've yet to find an AI that can handle this. The point is, any military units you make early on are long-term economic benefit you could have had instead.

The AI needs to factor in how well you're able to mobilize a powerful army from the ground up to crush their invasion. Not easy, I know, but when I have almost no military, but some powerful cities and technology, I laugh when I'm down on the bottom on power rating. Some AI decides it's time to be opportunistic, and yet gets wiped when all of my cities producing powerful units are mobilized against an invasion.

Early armies are not necessarily that much of an economic drain.  Only if you're trying to keep up with the Joneses will you run into financial trouble.

They have the benefit of providing experience for your champions and clearing out nearby lairs so that you can exploit resources.

When you don't need them any more you can disband them in cities that are still under their food cap for a small (but instant) population gain.

To be honest though I tend to move on to mid-game units quite quickly.  These are units designed with upgrading in mind, have their trait slots used up, have encumbrance calculated out in advance.  And they usually have mounts too.  You only need two such armies to lay waste to your enemy, or one and a half if you're really stingy.  The extra army provides relief for any units in the first army that have been injured, allowing them more time to heal back to full hitpoints.

I wonder that each city you settle add up 10 point in next turn and city that level up add 10 point in next level? or am I'm wrong?

Edit: I guess I'm wrong but for some reason city and city level, even some building like guardian do kick up a point...

Thanks to everyone who has replied so far, but no one seems to have the answer.  I was hoping that a modder who could read the code would know all the factors that go to make up Faction Power (FP) and their exact weighting, but perhaps that part of the code is not available or something like that, I don't know

If that is the case then we could get a good idea of what various things affect it by doing some tests on a known savegame position.  For instance I had a total of 1962 pop in my 9 cities and using the Death 5 spell Sacrifice I killed 1044 of them (gaining that much mana in the process).  You have to press end of turn for the FP to update. Next turn my FP dropped from 284 (without Sacrifice) to 242 a loss of 42 FP.  So population certainly does have some effect on FP and it seems to be about 4% of the pop.

Next I disbanded 3 units of level 8 Krax spearmen and the FP next turn dropped 5 FP so these units were contributing nearly 2 FP each.  By this process of elimination I should be able to get a fair idea of what the effects of things like unit level, total attack, total HP, defence, maintenance have on FP (if at all). I don't have a very good variety of units in my game at present so I stopped there. But this would be a tedious and error prone process anyway and that's why a code reader would do a much better job

JJ

You guys are all just guessing.  Faction Power is a random number generator.  I have a custom race that produces a lot of influence.  I get a huge lead in the Faction Power ratings and I have 0 troops.  I then ally with all the other factions and win the game never making a single troop.

P.S.  Whenever I play Magnar, I always start off dead last in Power Rating for most of the game even though I have good troops and cities.  Go figure.

I think city militia and archers count towards your FP.  It would make sense.

I've started scratching my head about faction power. I was playing my last Legendary Heroes game with Altar. For the longest time my faction power rating was 1st or 2nd, Magnar being a few points behind or ahead from time to time until we reached a score of ~185 each, with Resoln and Gilden being quite a way behind.

Suddenly out of the blue Magnar's faction power jumped to something like 2700. WTF moment. I decided at this point I had to take him down a peg or two, so I built some armies for 2 more of my heroes (other than my one champion stack) and went on a rampage across Magnar lands, effortlessly capturing or razing his cities. 

Some 2 hours of game time later my faction power is 560, and Magnar's is 50. I have reached the end of the tech-tree by this stage, and built several of the towers for the master ending. This may, or may not have boosted my rating. So may the cities I conquered and held. Yet on one or two occasions when I conquered a town, I saw no change. I haven't kept my eye on the power-meter throughout, you can tell ...

But WHAT was that 2000+ jump in faction power all about? And where have those power points gone? I'd really like to get a handle on this, since the rating clearly has an influence on diplomacy, yet how to manage this rating is shrouded in mystery.

That 2000 jump is regarding gold supply. I accidentally found out when the tribute system bugged and gave me a million gildar one turn. I spiked to something like 200000 next turn, before going down to normal the next one. It kept spiking like that whenever I got more gold. I'm not sure exactly how it's calculated, but money fluctuations seems to be the key.