taking down enemy planets

Well, there is the obvious one of going to war with them. If a minor and they are not allied with anyone, this should not be a problem and early in their life they are very vulnerable - except for the Minors that start out at the beginning of the game. At that point, everyone is vulnerable, but there are no transports ususally to worry about being invaded. With Majors, you want to sneak in the transports while their ships are busy doing something else. You may need multiple of them and some say that stacking the tranports helps. I have tried stacking, but not sure I see any difference between that and sending them in one at a time. The battle just goes faster.

Depending on the condition of the AI, sometime you can trade for one of their planets. This does not happen often, but if you really defeat them and they have lots of plantes, they will sometime give you a weak planet.

Culture flipping is the most common way to get planets without going to war.

~SDC~

The influence points you trade for have to do with the UP. The more points you get from them the less their vote counts, and the more yours does.

~SDC~

thanks, I was also wondering once you land the troops on the planet which battle tactic do you guys use? I've used core explosion.

When I do use troops to take a planet, I use convention warfare to minimize damage to the infrastructure. I have tried the other and cannot seem to make as much progress.

~SDC~

Yep, traditional warfare seems to be the most logical move, but if u have lots of cash to spend, many unhappy citizens on the other side, Information warfare could be deadly to the AI as well. LOL

Or, if you have cash and multiple transports and want to conserve troops, land one or two with Core Detonation and finish them off with conventional warfare.

~SDC~

I'm always wary about harming the planet so I generally go for traditional warfare. If it looks like I'll need help I'll go for information warfare (if it gives anything) and microsoldiers.

The best invasion tactic to use that is pretty cheap, gives a good advantage, and doesn't wipe out a planet is Gas Warfare. I use it to take heavily defended planets or when I don't have enough troops to do the trick conventionally. You'll still have a drop in quality, but usually not very bad (certainly not Mass Drivers or Core Detonation!)

A good way to get transports for invasion is to trade the AI for theirs. I do this all the time. The AI is usually stingy about trading techs for their transports, but if you manage to get a military tech before them (Corvette, Battleship, etc) they are more than willing to hand over a couple, if not all, of their transports/Combat Transports to you. You can even get some combat ships like Corvettes, Battle Cruisers this way. I like to trade the AI for their own invasion fleets, since the transports come fully loaded with troops (which also lowers the defenders on the planet). I know this is a cheesy tactic, but it's quicker and more enjoyable than culture flipping (which I hate...boooooooring).

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One side effect of this that I noticed - as long as the first attack fails, you don't end up damaging the planet Or maybe I've just been lucky when I've tried it? Of course, sometimes you miscalculate and win on the first battle, and then you cream the planet

When the attack fails there is NO resulting damage to anything but the population. I've been attacked alot and the AI uses every tactic they can afford to level the playing field (works about 1% of the time for them), I never recieve the ill effects unless they actually win.

If you have a pop advantage just go with traditional warfare the whole way and fire out alot of combat transports. Also, if you're wondering what to research, the soldiering bonus techs can really pile up, I've seen over 100 times advantage becuase of various bonuses.

I tend to like Gas Warfare. It's a nice compromise between power and conservation. Plus, I don't always have the cash on hand to use the big attacks. I'd love to use Information Warfare, but I can never seem to scrape together 2200 at the right moment.

I think the lack of damage to a planet when an invasion fails is proabbly an oversite that needs to be corrected.

Also are you sure transports come fully loaded? I play traders and I bought some transports figuring I could dump them on my worlds to boost population, but they always seem to be empty.

No,no,no,no!
Tidal Disrupters! No drop in planet quality!, But ok a few improvements destroyed but dose that really matter?
plus you get a warfare advantage of about 30-40% im not sure

Mine do...they're not always fully loaded, but they always come with troops.