Should enemies invade, they will first transit from the orbit area to the ground in assault pods. The space port and planetary defense units will be firing at them during that stage and they hit pretty hard, especially once your planetary defense units are upgraded. Those that survive will then engage the ground forces. There are a series of calculations that compare the relative forces on each side and list the bonuses above. I'll show that in another screen shortly.
You can watch the combat unfold, maximize it, minimize it, do other stuff and select other units while the combat screen remains open, etc. While combat unfolds you can see the units shooting at each other and who is taking damage. You can mouse over each unit to see its information and current strength.
