I've read the wiki article and I understand the different strengths of the units as well as the fact that 4 battalions make a brigade and 4 brigades make a division. Here are a few things I don't understand yet:
- How do you know if enemy troops are present on a planet before you land, and how many, what types?
As far as I know, you can't.
- I'm going to land a force on a planet with an alien ruin and have no idea if there are troops defending it, or how many defenders might emerge. Is this a good initial force to land there: 3 mobile infantry, 1 replacement battalion, and 1 brigade HQ? I have three troop carriers with 5 battalion capacity each.
That is rather light to defend when opening up ruins. I usually drop a couple of divisions of troops + some replacement battalions before dropping in the engineers. There shouldn't be troops waiting prior to opening the ruins though.
- What's the difference between a construction battalion and combat engineers? The wiki seems to use the terms interchangeably. Is a construction battalion sufficient to crack open the alien ruin?
The terms are used interchangeably on the wiki and by most players because they used to be the same unit, the Engineering Battalion, they were split in version 6.0. I don't think anyone has gone through the wiki to make clarifications since the split.
Construction Battalions have low combat ability but provide construction capability in the same way as a factory for use in the industry tab of the colony they are on. They are also used to open up ruins. Each unit is the size of a full battalion of other troops.
Combat Engineers have good combat ability and have their combat strength doubled when defending/assaulting a PDC.