A couple of things. First, though it's been pooh-poohed on this message board before, it's very important to keep your population as high as possible. That means keeping taxes quite low for a long time and researching farming techs up to the max. A planet might have 50% approval, but if it's also got 30 billion people, it's practically invincible. There are ways to keep planets from ever rebelling, no matter what the approval rate. I've had planets at 50 billion people at 10% approval for a couple of months, and it's been fine.

Second, the soldiering bonus is wonderful. I play a custom race, which gets 20% soldiering at the start, and then I research all techs that increase the soldiering bonus. When you invade another planet with that advantage, you can have 3 billion take out 11 billion easily. You'll notice that your enemies can't do that, even though you're disappointed that the bonus doesn't always work as you'd expected. In my current game, I've had the Torians, with a far superior military, invading my planets for months now. They haven't taken one yet. My population is always high, and the huge soldiering bonuses, though not giving me the ultimate advantage when invaded, have given me enough that they just can't get over the hump to take a planet. So, I'm surviving in an environment in which the Torians totally control the space around all my planets (huge galaxy). That's just from pop and soldiering. In other words, don't take it lightly. Sure, I'd love to control space, but since I've just fought a terrible war to wipe out the Yor, I have to fall back entirely on defenses at this point. If I didn't have the pop and soldiering bonuses, this game would have been over long ago.

I'd love to hear comments from those who have different strategies on this. However, those who say, "Don't let a planet get over 20 billion pop," or whatever their number is, probably haven't had to deal with this kind of total domination from an opponent's military. Sometimes it's only population that will save you, and that you will eventually parlay into outstanding invasion forces.

It's great when you're the one doing the invading. 1000 troops can take out several times their own force if the AI hasn't been johnny on the spot at researching its own soldiering bonuses.

I agree, getting all the techs as well as Tir-Quan is important. I usually keep my pop to the 15B limit with 100% approval. The high soldiering doesn't make me invincable by any means, but it certainly increases my odds.

My opponent spends 2, 3 or even 4 transports taking one of my planets while I've taken pretty much one of his planets for every transport I have. Also when he does finally take one of my planets he doesn't usually put a combat ship in orbit immediately so I can send a transport right back and re-take the planet.

I use a single advanced troop module per transport and fill it with 2000M troops. This allows quite a bit of space for engines so I usually have quite a bit of range on my opponent. You can pick off a number of undefended planets deep in his territory this way. I also generally use only one 2000M transport against all planets up to 10B with pretty good expectation of winning. I almost always use the mini-soldier invasion tactic. It cost 500bc but it minimizes the number of troops I need. It may destroy a building or two but it won't damage the planets PQ. Just be careful if the planet contains a wonder or trade good that you want.

Right. With high soldiering means less troops to take a planet, meaning smaller and cheaper ships. I use strictly tiny-hulled invasion craft. Advanced Troop Mod and some engines. One per planet. If I need more troops, information warfare.

It's funny how differant people take drastically differant approaches. I usually build ships that have 4-8 billion troops on them. I ship them from by high population base planets, then once they land the colony that I conquer is virtually fully populated. It limits my ability to crank them out in a pinch, but they work like gang busters, and practically negate any soldiering bonuses (due to the quanity of troops). I guess that's the beauty of the game, everyone has thier own style that works.

I beat the hell out of the AI with my feets and kill any ship they build before they can use it. then I slowly take each planet one by one, has never failed me. I play on masochistic and crippling and use 1000m troop ships.

I use tiny hulled ships to invade as well. Since you always lose at least one ship, it's the cheapest way. Most of the time you'll find the planet you capture has enough military production stored up to immediately replace the lost ship. Also allows you to invade with absurd numbers of troops so you'll never lose more than a handful and don't have to spend a penny on invasion tactics.

Downside is they're quite a bit slower, but that only really holds you up when you're first assembling the fleet. Once you've done that, you can replace them right on the front line since they're so cheap, so the low speed isn't an issue. I use larger transports as ferries to get people out from the heavily populated core worlds to the newly captured worlds.

I love threads where the starter asks a question but every poster just writes offtopic and wont answer anything.

He did NOT ask how to defend planets.

He did NOT ask how to invade planets.

He did NOT ask what games you are usually playing.

He did ask WHY the AI can invade his planets despite of the fact he got far superior soldering and technology.
There are a few reasons:

The exact power of your troop is randomed before each battle. this is what you call a "slot machine". so you might end up with a bad result.

The Attacker always gets a bonus in a battle.

The AI probably used some invasion tactic which gives him another bonus but this may damage the planet alot.

Your planet may have low population if the AI keeps attacking it. as the population determines the number of your troop in a battle, you might loose a battle even with superior soldering.

I love threads where the starter asks a question but every poster just writes offtopic and wont answer anything.

Good for you, Bodyless. You've added one detail, the roll-aspect of combat, to an answer that was being fleshed out from the very first reply, yet you sure want to appear to be the only one here who can or will answer the question. In the words of Ozzie Guillen, "Psht, please!"

Personally I thought his question was answered in the first post!

And i felt like there were still things to mention.

Good for you, Bodyless. You've added one detail, the roll-aspect of combat, to an answer that was being fleshed out from the very first reply, yet you sure want to appear to be the only one here who can or will answer the question. In the words of Ozzie Guillen, "Psht, please!"

It would have been alot easier to give a full answer or to add missing details and for other people to look for the answer if they have the same problem if there would not be that many flaming posts. Instead some are writing about things noone wanted to know. thats what is annoying me. if they want to discuss invasion and defending tactics why dont they make a new thread?!

Also the first post which tried to answer the question looked incomplete to me. and i added more than just one detail.

I always find it curious that so many write the words "no one" as noone.