Invasion
From Galactic Fleets Wiki
Invasion Invasion is when you have your warships and transport to claim a planets as your own. You would require troops inside and warships as support. Troops are not the only thing you can use during attack, bombers and fighters can also be bringed. Bombers can destroy or damage buildings.
When invading, warships are the first line of defense against invasion, you will need to eliminate them first. After the warships are destroyed, you will land on the planet and a battle will begin. To do this, select the transports(full of troops) and warships that you want it to participate in the invasion, and then click the "invade planet" button.
To have the planet as your own, you must eliminate all the troops on the planet and defending civilians. See Approval. Depending on the approval on your enemy planet, a faction of civilian will defend. Each 100 civilian equals to 1 troop.
You may fail the attempt and if you do, the same number of civilian will step up to fight against you. To fully claim the planet, you will need to have all civilian and troops on it eliminated. If you actually failed to take the planet, you will lose all the troops in the invasion(no survivors of the battle).
If you have claimed it, then you have ownership of it. Although, the civilian approval will go the opposite way, meaning if the approval is 100%, then it will become 0% while 50% will remain 50%, and so on. See approval.
See claiming