How Do I Establish A Beachhead?
Q: When I attack an enemy planet, I tend to feel like a raider. I bring in a strike force from one of my planets, try to kill the enemy, and then send over more ships if I fail. With stronger enemy planets, sometimes I never feel like I really get a foothold on their planet. What can I do differently?
A: Establishing a beachhead can be relatively simple or quite difficult, depending on the strength of the enemy on the planet. In any case, what you want to do is bring your strike group into the enemy planet, but not take them far from the wormhole. Kill any enemy ships that come over to your strike group, but don't pursue them if they retreat. Once the wormhole area is free of any enemies in the direct area, you may still be taking fire from long range missiles (usually from cruisers), and you're probably also taking fire from Snipers or Sniper Turrets.
This is when you bring in a Mobile Builder, and quickly build at LEAST a Counter-Sniper Turret. If you've also unlocked Counter-Missile Turrets, and are taking missile fire, build one of those, too. If you don't have Counter-Missile Turrets, send out some Fighters to take out the Cruisers that are firing those missiles. As soon as your Counters are up, you'll want to build at least one Space Dock, and probably also some short-range turrets to aid in the defense. Who says Turrets have to be used only in defensive positions? You can even build a bunch of Sniper Turrets yourself, and slowly whittle away on key enemy targets (Warp Gates, etc).
Once you have your foothold established, it's just a matter of holding it, and then attacking the nearby command posts of the enemy. You'll gradually weaken the enemy with each command post you take, so it's all about persistence if it's a particularly challenging planet.
Important: To establish a beachhead on a planet, you must have Supply at that planet. Therefore, you can only create beachheads on planets adjacent to those you control. So if a high-level enemy planet is way out in the middle of enemy territory, first try to take a lower-level planet next to it, then use that as a launching point for your true beachhead on the stronger planet.