I know that invading seems pretty easy (now and in the Beta). I'm not sure how much this has to do with the difference between soldiering vs non soldiering bonuses / Race bonuses & penalties. It could be a big difference...

The other consideration is the concept of Air Superiority. As you may know, there is a huge advantage built in to the invading force due to the fact that they MUST have air superiority, since they can only invade after the defending fleet (if any) has been defeated. Just like in real life, having air superiority is a huge advantage in both offense, defense (avoiding casualties) and intelligence (amplifying your own offense and defensive capabilities).

So 20% soldiering, Air Superiority, no planetary defense, only 65% resistance (sure how much this matters) and an attacking force of about 36% of the defender's force. That gave you 100% chance to succeed. Remember you are attacking with 2.5 billion soldiers, so assuming the game only goes down to tenth place digits, that leaves you with 100 million soldiers alive (2.5 -> 0.1). In other words, even if the defender killed 2.4 Billion soldiers, you would still have a 100% chance to succeed. I don't know the exact mechanics, so take this part with a grain of salt. I assume there is a standard deviation involved, so even with the variation in soldiers your opponent can kill, it is still >= 0.1 remaining.

Now comes the question, "Does this make sense?" In this case I would say it's not unreasonable. You basically have to have each of your soldiers kill 3 defenders each. Given the advantages in soldiering, air superiority and the penalties your opponent has (no defense, 65% resistance), and the fact that this is futuristic warfare that involves great destructive / killing potential, 3:1 doesn't seem that bad. Still, I'd like to see what other people think.

The relative strength you mention is simply your population x soldiering bonus (which gives you 3), and the opponent's population bonus x resistance (which gives you 4.55, rounding up to 4.6). The ratio is approximately 1:1.5 invader vs defender. This is why I mentioned "does this make sense?".

So it clearly doesn't count air superiority (which I'm pretty sure is mentioned somewhere in the game itself as mattering). So if relative strength has any meaning, air superiority must be equal to a multiplier of at least 155% (3 x 1.55 = 4.65 ->4.7). It is probably more though since your invader casualty is 'low'.

Again it doesn't mean "INVADER WINS". It means that air superiority isn't being shown to us / calculated in the invading power number.

Theoretically none of you population are soldiers they are civilians, being attacked byYor soldiers. also Paul had mentioned in his developer stream that it also depends on how many tiles the planet has and  that the soldiers land on one tile and move across the map vs the planet population. They removed the visual of this because it was not clean and was confusing people and made a simple interface until they were ready to make a cleaner more precise invation system and screen in a patch.

He did say that not only did planet defence represent soldiers on the planet but it represented the casulties the virtual drop ships would take invading the planet.

When I have any sign of invasion starting to happen I up my planet defence and make sure my people are happy .I have been able to hold off invasions to my planets by doing this. If you have a sensor boat you can see the slow moving invasion ship coming a mile away.

I don't think the invasion is broken its just that we are not seeing all that goes on during the invasion with this interface.

I myself liked the take one tile at a time watch the pop and soldiers die screen they had in beta but alot of beta testers did not .

Try that invasion again with 40 planetary defence and your population happy and the Yor would have lost, better yet distroy the invasion fleet in space first.